1 Thessalonians 4:3

"For this is the will of God, even your sanctification." And observe how he nowhere so vehemently glances at any other thing, as at this. As elsewhere also he writes to this effect; "Follow after peace with all men, and the sanctification without which no man shall see the Lord." (Heb. xii. 14) And why dost thou wonder, if he everywhere writes to his disciples upon this subject, when even in his Epistle to Timothy he has said, "Keep thyself pure." (1 Tim. v. 22) Also in his second Epistle to the Corinthians he has said, "In much patience, in fastings, by pureness." (2 Cor. vi. 5, 6) And one may find this in many places, both in this Epistle to the Romans, and everywhere, and in all his Epistles. For in truth this is an evil pernicious to all. And as a swine full charged with mire, wherever he enters, fills all places with his ill odor, and chokes the senses with dung, so too does fornication; it is an evil not easy to be washed away. But when some even who have wives practice this, how excessive is the outrage! "For this," he says, "is the will of God, even your sanctification, that ye abstain from all fornication." For there are many forms of disorderly conduct. The pleasures of wantonness are of many kinds and various, it were not tolerable to mention them. But having said "from all fornication," he leaves it to those who know them.