Notwithstanding their [the 1st century Christians of Asia Minor’s] loyalty to the head of state combined with adherence to Christianity, the principle—one must obey God rather than man—was understood by them in concrete situations as meaning that the Church is superior to the state any time a claim dangerous to the fundamentals of the Church demands such a decisive delimitation of authority.
“God is greater than the emperor”, was the claim of the Church of the martyrs as she courageously faced the threat of death.
[Chruch Father] Ambrose [of Milan] said frankly, before an imperial tyranny even when it had become Christian, in a phrase that was never forgotten in subsequent centuries and which became a classic formula:
“The emperor is in the Church, not above her. A good emperor seeks to help the Church not to combat her. We say this with a humility equal to our determination, even when threatened with torture, execution, or exile. As servants of Christ we put aside all fear.”
Rahner, H., translated by Davis, L.D. (1992) Church and State in Early Christianity [ebook]. Ignatius Press, San Francisco. Location 71 of 5067