From the Title On Betrothals, Second

Chapter IV. (The same, to the Bishop of Lucca). Just as a simple vow impedes a marriage to be contracted, but does not dirime one contracted, so the reception of the habit, without profession and renunciation of one's property, impedes lest one be contracted, but by no means dissolves one consummated.

Chapter VIII. (Ascribed to Hadrian IV, to Eberhard of Salzburg). According to the word of the Apostle, in Christ Jesus neither a free man nor a slave is to be removed from the ecclesiastical sacraments. Thus also among slaves marriages ought in no way to be prohibited; and if they shall have been contracted against the will and contradiction of their lords, by no reason are they on account of this to be dissolved by ecclesiastical law; nevertheless the due and customary services are not on this account any less to be rendered to their proper lords.

Cf. Canon XXX of the Second Council of Chalon, A.D. 813.

It is permitted to add the following from the Decretals, Book IV, Title 11, c. 2, of the same Alexander III to the Archbishop of Salerno.

If a man or woman, knowingly or ignorantly, shall have received his or her own child from the sacred font, and because you wished to consult us whether on account of this they ought to be separated from one another and coupled to others, we respond to your consultation in this manner: although it has generally been instituted that they ought to be separated, nevertheless certain persons, judging more humanely and more rightly, have established otherwise. Therefore it seems to us that, whether they have done this from ignorance or from malice, they are not to be separated from one another, nor ought either to subtract the debt from the other, unless they can be induced to observe continence; because if this was done from ignorance, ignorance seems to excuse them; if from malice, their fraud or deceit ought not to support them.

Malice, namely, consists in this, that a spouse knowingly receives his own child from the sacred font to this end, that he may be separated from the other spouse. The Pontiff does not wish this fraud to support the same one; accordingly he denies that they are to be separated.