22. If, therefore, even they who are united in marriage only for the purpose of begetting, for which purpose marriage was instituted, are not compared with the Fathers, seeking their very sons in a way far other than do these; forasmuch as Abraham, being bidden to slay his son, fearless and devoted, spared not his only son, whom from out of great despair he had received save that he laid down his hand, when He forbade him, at Whose command he had lifted it up; it remains that we consider, whether at least continent persons among us are to be compared to those Fathers who were married; unless haply now these are to be preferred to them, to whom we have not yet found persons to compare. For there was a greater good in their marriage, than is the proper good of marriage: to which without doubt the good of Continence is to be preferred: because they sought not sons from marriage by such duty as these are led by, from a certain sense of mortal nature requiring succession against decease. And, whoso denies this to be good he knows not God, the Creator of all things good, from things heavenly even unto things earthly, from things immortal even unto things mortal. But neither are beasts altogether without this sense of begetting, and chiefly birds, whose care of building nests meets us at once, and a certain likeness to marriages, in order to beget and nurture together. But those men, with mind far holier, surpassed this affection of mortal nature, the chastity whereof in its own kind, there being added thereto the worship of God, as some have understood, is set forth as bearing first thirty-fold; who sought sons of their marriage for the sake of Christ; in order to distinguish His race after the flesh from all nations: even as God was pleased to order, that this above the rest should avail to prophesy of Him, in that it was foretold of what race also, and of what nation, He should hereafter come in the flesh. Therefore it was a far greater good than the chaste marriages of believers among us, which father Abraham knew in his own thigh, under which he bade his servant to put his hand, that he might take an oath concerning the wife, whom his son was to marry. For putting his hand under the thigh of a man, and swearing by the God of Heaven, what else did he signify, than that in that Flesh, which derived its origin from that thigh, the God of Heaven would come? Therefore marriage is a good, wherein married persons are so much the better, in proportion as they fear God with greater chastity and faithfulness, specially if the sons, whom they desire after the flesh, they also bring up after the spirit.
Gen. xxii.12 Gen. xxiv.2-4