Did the early Church accept slavery?

Ignatius of Antioch d. c. 110 ADLetter to Polycarp 4.3

Do not be haughty toward slaves, male or female; but neither let them be puffed up. Let them serve all the more for the glory of God, so that they may obtain a better freedom from God. Let them not desire to be set free at the common expense, so that they may not be found slaves of desire.

"At the common expense" shows that churches sometimes paid to free slaves. Ignatius discourages slaves from expecting it.

Lactantius c. 250–c. 325 ADDivine Institutes 5.15

And there is no other reason why we give one another the name of brothers, except that we believe we are equals. For since we measure all human things not by the body but by the spirit, although the condition of bodies is different, we nevertheless have no slaves, but we both regard and call them brothers in spirit, fellow slaves in religion.

Lactantius answers an imagined objector who points to rich and poor, slaves and masters among Christians. He does not claim the legal institution had disappeared; his claim is how Christians regard and name one another.

Gregory of Nyssa c. 335–c. 395 ADHomilies on Ecclesiastes 4, on Ecclesiastes 2:7

"I got me slaves and slave girls" (Ecclesiastes 2:7). What do you mean? You condemn to slavery a human being, whose nature is free and self-governing, and you make laws against God, overturning his law for nature. ... "I got me slaves and slave girls." For what price, tell me? What did you find among existing things worth as much as this nature? For how many obols did you value the image of God? For how many staters did you sell the nature God shaped? ... Only God could do this; or rather, not even God himself.

A Lenten sermon about 379. It is the only surviving ancient text that condemns slave-owning itself, not just its abuses.

John Chrysostom c. 349–407 ADHomilies on 1 Corinthians 40.5

The race of slaves was not brought in for any need, since a slave would have been created along with Adam if it had been; it is the penalty of sin and the punishment of disobedience. ... So it is not necessary to own a slave; if it is necessary at all, let it be only one, or at most a second. ... For if you really cared for them, you would not keep anyone busy in your service, but would buy them, teach them trades so that they can support themselves, and let them go free.

From the moral exhortation (section 5) of Homily 40 on 1 Corinthians, against keeping retinues of household slaves for show. Chrysostom still permits one or two servants and treats slavery as a penalty for sin; his counsel to buy in order to teach and free goes beyond mere regulation, but it is not a call to abolish the institution.

Augustine of Hippo 354–430 ADCity of God 19.15

This name was earned by guilt, not by nature. The origin of the word servi (slaves) in the Latin language is believed to be derived from this: those who could by the law of war have been killed were kept alive by the victors and became slaves (servi), named from being spared (a servando). The first cause of slavery, then, is sin, by which man was subjected to man by the bond of a shared condition; this does not happen except by God's judgment, with whom there is no injustice, and who knows how to distribute different punishments according to the merits of offenders. But no one, by the nature in which God first created man, is a slave either of man or of sin.

Augustine denies that slavery is natural, against Aristotle: he treats it as a penal consequence of sin, imposed under God's just judgment, and he does not call for its abolition. The name servus, he says, preserves the memory that war captives who might lawfully have been killed were spared instead.