In his homily on the passage (Homily 18), John Chrysostom vividly illustrates Paul’s teaching, “You are not your own, for you are bought with a price. So glorify God in your body” (1 Cor 6:19b-20):
For supposing you had a daughter, and in extreme madness had let her out to a procurer for hire, and made her live a harlot’s life, and then a king’s son were to pass by, and free her from that slavery, and join her in marriage to himself; you could have no power thenceforth to bring her into the brothel. For you gave her up once for all, and sold her. Such as this is our case also. We let out our own flesh for hire unto the Devil, that grievous procurer: Christ saw and set it free, and withdrew it from that evil tyranny; it is not then ours any more but His who delivered it. If you be willing to use it as a King’s bride, there is none to hinder; but if you bring it where it was before, you will suffer just what they ought who are guilty of such outrages. Wherefore you should rather adorn instead of disgracing it. For you have no authority over the flesh in the wicked lusts, but in those things alone which God may enjoin. Let the thought enter your mind at least from what great outrage God hath delivered it. For in truth never did any harlot expose herself so shamefully as our nature before this. For robberies, murders, and every wicked thought entered in and lay with the soul, and for a small and vulgar hire, the present pleasure. For the soul, being mixed up with all wicked devices and deeds, reaped this reward and no other.
Truly, such sins are, as Chrysostom says, for such “present pleasure,” merely a “small and vulgar hire.” What mercy of Christ, who “saw and set [our flesh] free,” with nothing else but his own blood.