26 But, in order that it may be more clearly understood, how there may be virtue in habit, although it be not in work, I speak of an example, about which no Catholic Christian can doubt. For that our Lord Jesus Christ in truth of flesh hungered and thirsted, ate and drank, no one doubts of such as out of the Gospel are believers. What, then, was there not in Him the virtue of continence from meat and drink, as great as in John Baptist? For John came neither eating nor drinking; and they said, He has a devil; the Son of Man came both eating and drinking; and they said, “Lo, a glutton and wine-bibber, a friend of publicans and sinners.” What, are not such things said also against them of His household, our fathers, from another kind of using of things earthy, so far as pertains to sexual intercourse; “Lo, men lustful and unclean, lovers of women and lewdness?”
And yet as in Him that was not true, although it were true that He abstained not, even as John, from eating and drinking, for Himself says most plainly and truly, “John came, not eating, nor drinking; the Son of Man came eating and drinking:” so neither is this true in these Fathers; although there has come now the Apostle of Christ, not wedded, nor begetting, so that the heathen say of him, He was a magician; but there came then the Prophet of Christ, marrying and begetting sons, so that the Manichees say of him, He was a man fond of women: “And wisdom,” says He, “has been justified of her children.” What the Lord there added, after He had thus spoken of John and of Himself; “But wisdom,” says He, “has been justified of her children.”
Who see that the virtue of continence ought to exist even in the habit of the soul, but to be shown forth in deed, according to opportunity of things and times; even as the virtue of patience of holy martyrs appeared in deed; but of the rest equally holy was in habit. Wherefore, even as there is not unequal desert of patience in Peter, who suffered, and in John, who suffered not; so there is not unequal desert of continence in John who made no trial of marriage, and in Abraham, who begot sons. For both the celibate of the one, and the marriage estate of the other, did service as soldiers to Christ, as times were allotted; but John had continence in work also, but Abraham in habit alone.
Source: On the Good of Marriage (New Advent)