Ecclesiasticus 34:25

1. Cyprian to Quintus his brother, greeting. Lucian, our co-presbyter, has reported to me, dearest brother, that you have wished me to declare to you what I think concerning those who seem to have been baptized by heretics and schismatics; of which matter, that you may know what several of us fellow-bishops, with the brother presbyters who were present, lately determined in council, I have sent you a copy of the same epistle. For I know not by what presumption some of our colleagues are led to think that they who have been dipped by heretics ought not to be baptized when they come to us, for the reason that they say that there is one baptism which indeed is therefore one, because the Church is one, and there cannot be any baptism out of the Church. For since there cannot be two baptisms, if heretics truly baptize, they themselves have this baptism. …

Quietus of Baruch said: We who live by faith ought to obey with careful observance those things which before have been foretold for our instruction. For it is written in Solomon: “He that is baptized from the dead, (and again toucheth the dead,) what availeth his washing?” which certainly speaks of those who are washed by heretics, and of those that wash them. For if those who are baptized among them obtain by remission of their sins life eternal, why do they come to the Church? But if from a dead person no salvation is received, and therefore, acknowledging their previous error, they return to the truth with penitence, they ought to be sanctified with the one vital baptism which is in the Catholic Church.

18. Moreover also the blessed Paul not only welcomes Onesimus the unprofitable runaway thief, because he was converted, but also asks his master to treat him who had repented, on equal terms of honour with his teacher, thus saying: “I beseech thee for my son Onesimus, whom I have begotten in my bonds, who was aforetime unprofitable to thee, but now is profitable to thee and to me, whom I have sent back to thee; thou therefore receive him, that is my very heart, whom I would fain have kept with me, that in thy behalf he might minister unto me in the bonds of the Gospel; but without thy mind I would do nothing that thy goodness should not be as of necessity, but of free will. …

( Admonition 31.) Differently to be admonished are those who lament their transgressions, and yet forsake them not, and those who forsake them, and yet lament them not. For those who lament their transgressions and yet forsake them not are to be admonished to learn to consider anxiously that they cleanse themselves in vain by their weeping, if they wickedly defile themselves in their living, seeing that the end for which they wash themselves in tears is that, when clean, they may return to filth. For hence it is written, The dog is returned to his own vomit again, and the sow that was washed to her wallowing in the mire ( 2 Pet. ii. 22 ). For the dog, when he vomits, certainly casts forth the food which weighed upon his stomach; but, when he returns to his vomit, he is again loaded with what he had been relieved from. …

Now they are in the flesh who live in carnal pleasures. Against them it is said, Neither shall corruption possess incorruption ( 1 Cor. xv. 50 ). But, if they say that a short season of penitence may suffice against sin, so that one may be allowed to return again to sin, rightly does the sentence of the first pastor hit them, when he says, It is happened unto them according to the true proverb; The dog is turned to his own vomit again, and the sow that was washed to her wallowing in the mire ( 2 Pet. ii. 22 ). For great is the efficacy of penitence against sin; but only if one persevere in this penitence. For it is written, He that shall persevere unto the end, the same shall be saved ( Matth. x. 22: xxiv. 13 ). Hence again it is written, He that is baptized from a dead body, and toucheth it again, what availeth his washing? ( Ecclus. xxxiv. 30 ). …