NOTE: The early Church Fathers never criticized or condemned slavery. Early Christians and Christian writers accepted slavery as a necessary part of fallen man and justified it in the case of captives taken in war and criminals sentenced to slavery. Some of the popes and patriarchs owned slaves, and religious orders owned slaves; not one Orthodox hierarch or theologian of the early Church said slavery was intrinsically evil. Almost every Council of the Church—regional and ecumenical, in both Eastern and Western Christendom—discussed and regulated slavery but never condemned it nor sought, in any way, to abolish the institution.
Today, in the 21st century, the Orthodox Church still sanctions a form of slavery through the life of monasticism. The Ladder of Divine Ascent—also referred to as “The Monastic Bible”—states: “You who are therefore trying to lay your own burden on Another’s shoulders [i.e. via submitting in blind obedience to an Elder], you who are hastening to sign a pledge that you are voluntarily surrendering yourself to slavery” (Step 4:5). At the end of the book, St. John Climacus writes his own Beautitudes for monastics: “Blessed is he who is as zealous with true zeal as a well-disposed slave towards his master” (Step 30:11).
The following article is taken from The Rudder, pp. 237-238; 391-393
APOSTOLIC CANON LXXXII (82)
We do not permit house servants to be ordained to the clergy without the consent of their masters, to the sorrow of the masters owning them. For such a thing causes an upheaval in the households. But if any house servant should appear to be worthy to be ordained to any rank, as our own Onesimus did, and their masters are willing to permit it, and grant them their freedom (by liberating them from slavery), and allow them to leave home, let him be so ordained. (Canon IV of the 4th Ecumenical Synod; Canon LXXXV of the 6th Ecumenical Synod; Canon III of Ancyra; Canon XC of Carthage; Canons XL, XLI, XLII of Basil; and the Epistle to Philemon)
One must not do things that become causes of scandal or of sorrow to others. One cause of scandal, of course, and of sorrow is that which results whenever a slave is ordained without the consent of his own master. Thus the present Canon prohibits this, stating: We do not allow slaves to be promoted to the clergy and Holy Orders without the consent of their masters, lest we cause sorrow to the masters themselves by doing so. Because this sort of thing upsets whole households (for it might happen that the slave admitted to the clergy was either the manager of his master’s household, or the superintendent of his factory, or had the care of his master’s money; and on all such accounts his ordination might cause his master grief).
But if any slave should appear to be worthy for ordination, as did our own Onesimus, the bishop ought to notify his master to this effect, and if the latter consents and is willing, and at the mouth of two or three witnesses according to the LXXXV of the 6th Ecumenical Synod, and sends him home as a sign of total liberty, then let him be ordained. That is what St. Paul did, since he refused to keep the slave Onesimus, and in spite of the fact that he found him to be very useful in the ministry of preaching, he sent him back to his master Philemon.
Nor must slaves be admitted to monasteries to become monks without the consent of their masters, according to Canon IV of the 4th Ecumenical Synod. And any female slave who gets married without the consent of her master has thereby become guilty of harlotry, according to Canons XL and XLII of St. Basil; for according to him, agreements and promises made by vassals are unreliable. And according to his Canon XLI any marriage that takes place without the consent of the master of a female slave must be dissolved if he does not want it. That is why the synod held in Gangra anathematizes in its Canon III anyone who on the pretext of piety teaches a slave to hold his master in contempt and to leave his service. According to Canon LXXIII of Carthage, the freedom of slaves ought to be preached in the churches.115
Footnote 115 on the Apostolic Canons
Note that there are four distinct types of vassals according to the laws. They are either fortuitous, as slaves to their masters; or naturally such, as children to their parents; or by matrimony, as a wife to her husband, and, conversely, a husband to his wife; or by census, as civil officeholder to generals of the army. Some authorities add a fifth species of vassalage, which they call spiritual subjection; such is that of subordinates to their elders in the monasteries. As concerns the vassalage of a wife to her husband, and of a husband to his wife, see the footnote to Canon XLVIII of the 6thEcumenical Synod. Concering the vassalage of children to their parents. See the footnotes to Canon XXVII of the 4th Ecumenical Synod, to Canon XLII of Carthage, and to Canon XXXVIII of Basil. As concerns the vassalage of slaves to their masters (and in part that of vassalage which soldiers owe to army leaders), it is of that kind of vassalage that we are speaking of here. Novels 9, 10, and 11 of Leo the Wise prescribe that any slave who becomes a clergyman or a monk or a bishop without his master’s knowledge, if he is a fugitive from the latter for not more than three years, he is to be searched for by his master, and when found he is to return again to his former lot and be a slave; but if he was known to his master to have been admitted to the clergy or to a monastery, it prescribes that he is to be searched for not more than a year.
Photios, on the other hand, in Title I, Chapter 36, says that according to ordinance 36 of Title III of Book I of the Code, a slave even with his master’s consent cannot be admitted to the clergy unless he first is liberated.
The second ordinance of Title I of the Novas decrees that if when a slave was being admitted to the clergy his master knew about it and offered no objections, the slave is liberated ex ipso facto. And Michael Attaliotes in his Synopsis, Title III, says that as soon as a slave was ordained he became a free man if his master knew about it and remained silent. The same ordinance says that the episcopate liberates slaves from the authority of their masters and soldiers from that of their generals, provided it is conferred upon them with the consent of those who have control over them. Note further that the law says that if anyone is asked and offers no objection, but keeps silent, in case the matter concerning which he is asked is one to his profit or advantage, he will be considered to have given his consent to it; but if it be one to his loss or disadvantage, he will be considered to have refused.
Nevertheless, when anyone is aware of the ordination of his slave, and fails to offer any objection to it, notwithtanding that it is to his disadvantage or damage, he will be regarded as having given his consent to it; and this applies specifically to the liberty of the one admitted to the clergy, that is to say. Thus it is written in the scholium (or comment) of Balsamon on the text of Title I, Chapter 36, of the Nomicon of Photios. Furthermore, according to Armenopoulos, Book I, Title XVIII, a slave is accorded his liberty in case his master dies without leaving a will. If anyone is rich and is bought by the enemies, he is to pay his price and be bought back. But if he is a poor man, he is to slave for three to five years for the one who bought him, and thus he will gain the right to be liberated. Any slave, again, is automatically freed and set at liberty if he became a soldier, or a monk, or a clergyman, and his master was aware of it.
Those slaves, on the other hand, who abandon the ascetic mode of life after having become monks, and go to another state (or political domain), are to become slaves again, according to Book 4, Title I, Chapter 11, subject 13. (See also the footnote to Canon V of the lst-&-2nd Synod, and Armenopoulos, ibid.) Note further that there are two kinds of slaves: some are born slaves, and these include all who are born of women who are slaves; and others become slaves when they are captured by enemies at war. Those, on the other hand, who are slaving, or working, for their masters for wages or for a salary, are not properly speaking slaves, but obviously are only hired men or employees. Concerning this latter class of men, divine Chrysostom (Sermon 4 to Titus) says that anyone deserves to be blamed if under the pretense of temperance or of continence he divorces wives from their husbands, and slaves from their masters. Sirach, finally, says: “Let your soul love a house slave of understanding, and deny him not his freedom” (Ecclesiastes 7:21).