The sun rose over Milan just as it had on every other day. But this Lord’s Day in 390 A.D. would be far from ordinary in the new imperial center of the Western Roman Empire. After a half century of religious tumult, the Roman Empire was finally at rest under Emperor Theodosius, a defender of the Nicene Creed. Yet, as he approached the church that day, the Bishop Ambrose blocked his path and took hold of the emperor’s purple robes in full public view.

“Stand back!” warned Ambrose, according to the fifth century eastern historian Sozomen. “A man defiled by sin, and with hands imbrued in blood unjustly shed, is not worthy, without repentance, to enter within these sacred precincts, or partake of the holy mysteries.”

In effect, Ambrose threatened not to serve communion with the emperor present. But what was he doing, denying Christian communion to the first emperor since Constantine to throw his full support behind the church? Who did Ambrose think he was?

The Thessalonian Incident

To understand this incident, we must first rewind for context. Both Ambrose and Theodosius were responding to events that occurred earlier that year in Thessalonica, the Macedonian city of biblical fame. There, according to Sozomen, a popular charioteer had been arrested after he “attempted an outrage” against the commander of the city garrison, General Butheric, while the general was “shamefully exposed” — which may suggest that the charioteer had made “an unwanted homosexual advance.” (Some celebrities have long felt a license to live however immorally they please.)

When Butheric refused popular demands to release the charioteer, the Thessalonians rioted, and Butheric was killed. (Fanaticism over sports is no modern phenomenon.)

News of the riot infuriated Theodosius, who ordered his troops to take vengeance in blood. The Roman army proceeded to indiscriminately massacre an estimated 7,000 Thessalonians in one day. Theodosius countermanded his order the next day, but it was too late. The emperor returned to Milan, and to Ambrose, but Ambrose left the city rather than be seen as supporting the emperor’s bloodshed.

“There was that done in the city of the Thessalonians of which no similar record exists … which you yourself show, by revoking it too late, you consider to be grave,” Ambrose wrote to the emperor in a private letter. He then warned the emperor he would not serve him Communion until he repented, “I dare not offer the sacrifice if you intend to be present. Is that which is not allowed after shedding the blood of one innocent person, allowed after shedding the blood of many? I do not think so.”

Prophetic Reproof to an Emperor

These are bold words from a cleric to an emperor. Yet Ambrose depicted himself as Nathan the prophet confronting a sinful David. “Are you ashamed, O Emperor, to do that which the royal prophet David, the forefather of Christ, according to the flesh, did?” he queried. “To him it was told how the rich man who had many flocks seized and killed the poor man’s one lamb … And, recognizing that he himself was being condemned in the tale, for that he himself had done it, he said: ‘I have sinned against the Lord.’ Bear it, then, without impatience, O Emperor, if it be said to you: You have done that which was spoken of to King David by the prophet.”

Ambrose urged Theodosius to pray to God for forgiveness, for “prayer by itself is a sacrifice, it obtains pardon, when the oblation would bring offense, for the one is a sign of humility, the other of contempt.” His letter struck at the heart of repentance. “Are they not, then, rather Christians in truth who condemn their own sin, than they who think to defend it? … He who accuses himself when he has sinned is just, not he who praises himself.”

As indicated above, Theodosius ignored the private letter from Ambrose and showed up to the church anyway. It was only after Ambrose publicly confronted him that “the emperor, struck with admiration at the boldness of the bishop, began to reflect on his own conduct, and, with much contrition, retraced his steps,” Sozomen described.

At this point, Theodosius could have responded in multiple ways. He could have exiled Ambrose, as his predecessors had so often done to Athanasius. He could have deposed him, reassigned him, executed him, or had him secretly murdered.

Instead, by God’s grace, Theodosius did respond to Ambrose’s prophetic correction like King David. He publicly confessed his sin in church, established a new law that postponed the enforcement of any imperial death sentence for 30 days, and set aside his imperial ornaments until Ambrose allowed him back into fellowship.

Pagan No Longer

Not long before, it would have been unthinkable for an emperor to humble himself in a place of religious worship and repent of sin. Former Roman emperors had made their subjects worship them as gods, and mere mortals may not question the actions of a divinity. In fact, combining religion and politics was a common method of enforcing obedience throughout paganism. Where kings were not explicitly worshiped, their authority was often tied to whatever gods were.

When the Roman emperors suddenly embraced Christianity, the connection between religion and politics was not immediately questioned. Constantine was a Christian, so he made his empire officially Christian, just as previous pagan emperors had ruled over an officially pagan empire. His Arian heirs made the empire Arian, while the orthodox ones defended Nicaea, and so forth.

But this worldly way of thinking did not align with Scripture. Jesus himself had drawn the distinction, “render to Caesar the things that are Caesar’s, and to God the things that are God’s” (Matthew 22:21). Or, more universally, “My kingdom is not of this world” (John 18:36). Ambrose was one of the first (if not the first) Christians to apply this teaching to church-state relations. He concluded, “the emperor is within the Church, not above the Church.” The two are not identical.

An Unlikely Bishop

The unusual insights of Ambrose may have stemmed in part from his unusual career. Born around 340 to a Praetorian prefect in Trier, Germany, Ambrose studied law in Rome and rapidly ascended Rome’s political echelon. By his early 30s, Ambrose had become the governor of northern Italy, at a time when Western emperors preferred to dwell in the pristine climes of Milan rather than unhealthy and overpopulated Rome. Ambrose was a competent and fair governor, and therefore a popular one.

It’s unclear when Ambrose came to personal faith in the Christian God, because it had already become an unfortunate practice to delay baptism until long after conversion. At age 34, Ambrose was still unbaptized, although he believed in God according to the Nicene Creed (of 325). Whatever the timeline, Ambrose had survived and even thrived amid the rapid turnover of emperors. But religious turmoil could still affect his job.

In 374, the bishop of Milan, who had been an Arian, died. This sharply divided the city between Arians and orthodox Christians over who would get to choose the next bishop. The dispute between candidates broke out into disorder within the basilica, and Governor Ambrose rose to quiet the crowds.

To his surprise, the crowds began shouting, “Ambrose for Bishop!” The orthodox faction saw in Ambrose the most popular representative of their views. But the Arians also chanted for Ambrose, calculating that the fair and just governor would at least be fair and just to them as a bishop. Ambrose declined the appointment, and he even ran and hid. But a letter from the Emperor Valentinian confirming him as bishop forced him to reluctantly accept the post. Ambrose was then baptized, as it would not do for a non-member of the church to be its ruler.

This Saul-like beginning could have been a bad sign of things to come. Based on 1 Timothy 3:1, “If anyone aspires to the office of overseer, he desires a noble task,” some Christians argue that a desire to become an overseer (or elder, or bishop) is a prerequisite to the office, and Ambrose certainly did not have such a desire.

A Fruitful Ministry

But, in God’s grace, Ambrose threw himself into the new role wholeheartedly. He embarked on an intense course of biblical study to make up for his lack of education on the matter. And, despite the steep learning curve, Ambrose became quite an able theologian. He vigorously suppressed Arianism in all churches under his authority — something the Arians did not count on when they supported his appointment. He authored a number of theological tracts, including one affirming the substitutionary nature of Christ’s atonement:

“And so then, Jesus took flesh that He might destroy the curse of sinful flesh, and He became for us a curse that a blessing might overwhelm a curse, uprightness might overwhelm sin, forgiveness might overwhelm the sentence, and life might overwhelm death. He also took up death that the sentence might be fulfilled and satisfaction might be given for the judgment, the curse placed on sinful flesh even to death. Therefore, nothing was done contrary to God’s sentence when the term of that sentence was fulfilled, for the curse was unto death but grace is after death.”

Ambrose also preached with sufficient skill and depth to impress an unconverted rhetoric teacher named Augustine. Augustine thought that the Bible was only for the ignorant and came to church only to hear Ambrose’s polished oratory, not his gospel message. But Ambrose’s exposition of difficult biblical passages so justified Christian doctrines that they finally began “to appear to me capable of defense,” Augustine later wrote in his “Confessions.”

“This man of God received me like a father, and as a bishop told me how glad he was that I had come. My heart warmed to him, not at first, as a teacher of the truth, which I had quite despaired of finding in your church, but simply as a man who showed me kindness,” Augustine recalled in prayer. “At that time his gifted tongue never tired of dispensing the richness of your word and the joy of your word. … Unknown to me, it was you, God, who led me to Ambrose so that I might knowingly be led by Ambrose to you.” Augustine would go on to surpass his mentor and become a giant of Christian theology.

The kindness with which Ambrose handled the unconverted Augustine illustrates how, whatever doctrinal controversies were in play, Ambrose’s heart always carried a pastoral bent. Before Augustine’s conversion, he comforted the man’s dutiful mother, Monica, “It is not possible that the son of these tears should perish.” He also sold most of his family estate (leaving enough to care for his unmarried sister) and melted down church ornaments to ransom captives taken during barbarian raids.

Ambrose also shared with Augustine a morsel of sound biblical wisdom that has come down through the ages in the line, “When in Rome…” Augustine’s mother Monica was distressed that the church in Milan did not fast on Saturday as the church in Rome had done. When Augustine (then unconverted) asked Ambrose about it, he responded, “When I visit Rome, I fast on Saturday; when I am here, I do not fast. On the same principle, do you observe the custom prevailing in whatever Church you come to, if you desire neither to give offence by your conduct, nor to find cause of offence in another’s.”

Pastor under Siege

But, whatever his other talents as a pastor, mentor, and theologian, Ambrose’s most enduring contribution is likely his insistence on distinguishing church from state — in his context, separating the Christian church from the Roman Empire. Ambrose’s first test came years before his public rebuke of Theodosius, under the Arian emperor Valentinian II and his Arian mother, Justina.

In 385-386, Justina ordered Ambrose to hand over certain church space in Milan for Arian worshipers, but he refused, arguing, “What belongs to God is outside of the Emperor’s power,” and “the temple of God could not be surrendered by a Bishop.” Justina “represented to her son that he had insulted her,” wrote Sozomenus, so that “he sent a party of soldiers against the church.”

“On their reaching the temple, they forced their way into the interior, arrested Ambrose, and were about to lead him into exile at that very moment, when the people assembled in crowds at the church, and evinced a resolution to die rather than submit to the banishment of their priest,” he continued.

There followed a confused standoff of uncertain length, with the Christian congregation (including Monica and Augustine) effectively staging a massive sit-in to deter the Arian authorities from seizing their bishop or their church. “I could not return home, because the soldiers who were guarding the basilica were all around,” Ambrose recalled.

Incidentally, this moment may have launched the whole tradition of hymn-singing in the West. “We passed that whole day in sadness,” said Ambrose. “We repeated Psalms with the brethren in the smaller basilica.” Ambrose composed a number of hymns over his life, which so surpassed those of previous Christians in quantity and quality that many found their way into Martin Luther’s hymnal, more than 1,100 years later.

The emperor ultimately decided he had more pressing political problems without provoking a riot in his capital by arresting the defiant bishop. He eventually ordered his soldiers to stand down, but not before complaining to an advisor, “If Ambrose bade you, you would deliver me up to him in chains.”

Skirmish with Theodosius

This successful effort of civil disobedience then became the backdrop for Ambrose’s later interactions with Theodosius. Two years before his public confrontation, Ambrose had already confronted the emperor over another imperial action.

In 388, a mob of Syrian Christians had burnt down a synagogue, and Theodosius had ordered Christians to pay for rebuilding it, and he ordered a general to intimidate Christian monasteries. Ambrose protested in a letter, arguing that Theodosius’s selected punishment was inconsistent with precedent and punished all Christians without discrimination. “Shall the patrimony, which by the favor of Christ has been gained for Christians, be transferred to the treasuries of unbelievers?” Ambrose wrote. “How great a thing it is, O Emperor, that you should not think it necessary to enquire or to punish in regard to a matter as to which up to this day no one has enquired, no one has ever inflicted punishment. It is a serious matter to endanger your salvation for the Jews.”

Theodosius ignored Ambrose’s letter. But, when he later came to church in Milan, Ambrose chose to preach on God removing Saul from his throne for murdering priests (1 Samuel 22:17). In a later letter, Ambrose related the exchange that followed. “When I came down from the pulpit, he said to me: ‘You spoke about me.’ I replied: ‘I dealt with matters intended for your benefit.’” That sermon induced the emperor to rescind his orders.

The merits of this earlier episode are less clear. But they did continue to lay the groundwork for a church independent of the Roman state, which could comment on the morality of its policies not based on the authority of any earthly ruler, but solely on the word of God.

A Legacy for the West

Two years later, the massacre in Thessalonica raised the stakes. Theodosius had committed a much worse sin. And Ambrose engaged in a bolder and more dangerous confrontation. But the Christian emperor proved his faith by repenting, “submitting to one another out of reverence for Christ” (Ephesians 5:21). And so, Ambrose’s legacy established a distinction between church and state.

While some Christian leaders in the eastern empire criticized political authorities to different degrees, they never had such a defining moment as Ambrose. Today, the Orthodox church remains more heavily influenced by political leaders.

That distinction between church and state led later generations of Christians to clarify the difference: the state wields the sword (Romans 13:4), while the church wields the keys (Matthew 18:18). Later still, this distinction even crossed over into political thought, such as the U.S. Constitution’s prohibition on any establishment of religion in the First Amendment, and its guarantee of religious freedom.

Ambrose would have agreed that religious freedom extended to pastors commenting on the morality of various public policies. Citing the instructions for Israel’s watchman from Ezekiel 3:18, Ambrose wrote, “If the priest speak not to him that errs, he who errs shall die in his sin, and the priest shall be liable to the penalty because he warned not the erring.”

“It is neither the part of an emperor to refuse liberty of speech, nor of a priest not to say what he thinks,” Ambrose argued. “This is the difference between good and bad princes, that the good love liberty, the bad slavery. And there is nothing in a priest so full of peril as regards God, or so base in the opinion of men, as not freely to declare what he thinks.”

These words make clear that Christian pastors must not simply repeat what the rulers want them to, but that they have a higher duty to God to declare the truth at all costs. Most fundamentally, this requires that the church be distinct and independent from the state.