Genesis 24:2

Isaac married Rebecca, the grand-daughter of Nahor, his father’s brother, when he was forty years old, that is, in the 140th year of his father’s life, three years after his mother’s death. Now when a servant was sent to Mesopotamia by his father to fetch her, and when Abraham said to that servant, “Put thy hand under my thigh, and I will make thee swear by the Lord, the God of heaven, and the Lord of the earth, that thou shalt not take a wife unto my son Isaac of the daughters of the Canaanites,” what else was pointed out by this, but that the Lord, the God of heaven, and the Lord of the earth, was to come in the flesh which was to be derived from that thigh? Are these small tokens of the foretold truth which we see fulfilled in Christ?

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. …

41. Besides this wonderful agreement between the types and the things typified, the adversary may be convinced by plain prophetic intimations, such as this: "In thy seed shall all nations be blessed." This was said to Abraham, and again to Isaac, and again to Jacob. Hence the significance of the words "I am the God of Abraham, and Isaac, and Jacob." God fulfills His promise to their seed in blessing all nations. With a like significance, Abraham himself, when he made his servant swear, told him to put his hand under his thigh; for he knew that thence would come the flesh of Christ, in whom we have now, not the promise of blessing to all nations, but the promise fulfilled.

For it must not be supposed that those saints of old only profited by Christ’s divinity, which was ever existent, and not also by the revelation of His humanity, which had not yet come to pass. What the Lord Jesus says, “Abraham desired to see my day, and he saw it, and was glad,” meaning by the phrase his day to understand his time , affords of course a clear testimony that Abraham was fully imbued with belief in His incarnation. It is in respect of this that He has a “time;” for His divinity exceeds all time, for it was by it that all times were created. …

16. “Your father Abraham rejoiced to see my day; and he saw, and was glad.” Abraham’s seed, Abraham’s Creator, bears a great testimony to Abraham. “Abraham rejoiced,” He says, “to see my day.” He did not fear, but “rejoiced to see it.” For in him there was the love that casteth out fear. He says not, rejoiced because he saw; but “rejoiced that he might see.” Believing, at all events, he rejoiced in hope to see with the understanding. “And he saw.” And what more could the Lord Jesus Christ say, or what more ought He to have said? “And he saw,” He says, “and was glad.” Who can unfold this joy, my brethren? If those rejoiced whose bodily eyes were opened by the Lord, what joy was his who saw with the eyes of his soul the light ineffable, the abiding Word, the brilliance that dazzles the minds of the pious, the unfailing Wisdom, God abiding with the Father, and at some time come in the flesh …

11. What does he mean to express by the “thigh”? The flesh. Whence those words, “A prince shall not depart from Judah; and a lawgiver from his thighs”? Did not Abraham himself (to whom was promised the seed in which “all the nations of the earth were to be blessed”), when he sent his servant to seek and to bring home a wife for his son, being by faith fully persuaded, that in that, so to speak, contemptible seed was contained the great Name; that is, that the Son of God was to come of the seed of Abraham, out of all the children of men; did not he, I say, cause his servant to swear unto him in this manner, saying, “Put thy hand under my thigh,” and so swear; as if he had said, “Put thy hand on the altar, or on the Gospel, or on the Prophet, or on any holy thing.” “Put” (he says) “thy hand under my thigh;” having full confidence, not ashamed of it as unseemly, but understanding therein a …