As if then we were banquetting with Christ Himself, and partaking of His table, let us do nothing at random, but let us pass our time in fastings, and prayers, and much sobriety of mind. For if a man who is destined to enter upon some temporal government, prepares himself all his life long, and that he may obtain some dignity, lays out his money, spends his time, and submits to endless troubles; what shall we deserve, who draw near to the kingdom of heaven with such negligence, and both show no earnestness before we have received, and after having received are again negligent? Nay, this is the very reason why we are negligent after having received, that we did not watch before we had received. Therefore many, after they have received, immediately have returned to their former vomit, and have become more wicked, and drawn upon themselves a more severe punishment; when having been delivered from their former sins, herein they have more grievously provoked the Judge, that having been delivered from so great a disease, still they did not learn sobriety, but that has happened unto them, which Christ threatened to the paralytic man, saying, “Behold you are made whole: sin no more, lest a worse thing come unto you”: and which He also predicted of the Jews, that “the last state shall be worse than the first.” For if, says He, showing that by their ingratitude they should bring upon them the worst of evils, “if I had not come, and spoken unto them, they had not had sin”; so that the guilt of sins committed after these benefits is doubled and quadrupled, in that, after the honour put upon us, we show ourselves ungrateful and wicked. And the Laver of Baptism helps not a whit to procure for us a milder punishment. And consider: a man has gotten grievous sins by committing murder or adultery, or some other crime: these were remitted through Baptism. For there is no sin, no impiety, which does not yield and give place to this gift; for the Grace is Divine. A man has again committed adultery and murder; the former adultery is indeed done away, the murder forgiven, and not brought up again to his charge, “for the gifts and calling of God are without repentance”; but for those committed after Baptism he suffers a punishment as great as he would if both the former sins were brought up again, and many worse than these. For the guilt is no longer simply equal, but doubled and tripled. Look: in proof that the penalty of these sins is greater, hear what St. Paul says: “He that despised Moses' law died without mercy, under two or three witnesses: of how much sorer punishment, suppose ye, shall he be thought worthy, who has trodden under foot the Son of God, and has counted the blood of the covenant an unholy thing, and has done despite unto the Spirit of grace?”
Perhaps we have now deterred many from receiving baptism. Not however with this intention have we so spoken, but on purpose that having received it, they may continue in temperance and much moderation. 'But I am afraid,' says one. If you were afraid, you would have received and guarded it. 'Nay,' says he, 'but this is the very reason why I do not receive it—that I am frightened.' And are you not afraid to depart thus? 'God is merciful,' says he. Receive baptism then, because He is merciful and ready to help. But you, where to be in earnest is the thing required, dost not allege this mercifulness; you think of this only where you have a mind to do so. And yet that was the time to resort to God's mercy, and we shall then be surest of obtaining it, when we do our part. For he that has cast the whole matter upon God, and, after his baptism, sins, as being man it is likely, he may, and repents, shall obtain mercy; whereas he that prevaricates with God's mercy, and departs this life with no portion in that grace, shall have his punishment without a word to be said for him. 'But how if he depart,' say you, 'after having had the grace vouchsafed to him?' He will depart empty again of all good works. For it is impossible, yes, it is in my opinion impossible, that the man who upon such hopes dallied with baptism should have effected ought generous and good. And why do you harbor such fear, and presume upon the uncertain chance of the future? Why not convert this fear into labor and earnestness, and you shall be great and admirable? Which is best, to fear or to labor? Suppose some one to have placed you, having nothing to do, in a tottering house, saying, Look for the decaying roof to fall upon your head: for perhaps it will fall, perhaps not; but if you had rather it should not, then work and inhabit the more secure apartment: which would you have rather chosen, that idle condition accompanied with fear, or this labor with confidence? Why then, act now in the same way. For the uncertain future is like a decayed house, ever threatening to fall; but this work, laborious though it be, ensures safety.
Source: Homilies on Acts (New Advent)