2. And Abraham said unto his eldest servant. Abraham here fulfils the common duty of parents, in laboring for and being solicitous about the choice of a wife for his son: but he looks somewhat further; for since God had separated him from the Canaanites by a sacred covenant, he justly fears lest Isaac, by joining himself in affinity with them, should shake off the yoke of God. Some suppose that the depraved morals of those nations were so displeasing to him, that he conceived the marriage of his son must prove unhappy if he should take a wife from among them. But the special reason was, as I have stated, that he would not allow his own race to be mingled with that of the Canaanites, whom he knew to be already divinely appointed to destruction; yea, since upon their overthrow he was to be put into possession of the land, he was commanded to treat them with distrust as perpetual enemies. And although he had dwelt in tranquility among them for a time, yet he could not have a community of offspring with them without confounding things which, by the command of God, were to be kept distinct. Hence he wished both himself and his family to maintain this separation entire.
Put, I pray thee, thy hand. It is sufficiently obvious that this was a solemn form of swearing; but whether Abraham had first introduced it, or whether he had received it from his fathers, is unknown. The greater part of Jewish writers declare that Abraham was the author of it; because, in their opinion, this ceremony is of the same force as if his servant had sworn by the sanctity of the divine covenant, since circumcision was in that part of his person. But Christian writers conceive that the hand was placed under the thigh in honor of the blessed seed. (2) Yet it may be that these earliest fathers had something different in view; and there are those among the Jews who assert that it was a token of subjection, when the servant was sworn on the thigh of his master. The more plausible opinion is, that the ancients in this manner swore by Christ; but because I do not willingly follow uncertain conjectures, I leave the question undecided. Nevertheless the latter supposition appears to me the more simple; namely, that servants, when they swore fidelity to their lords, were accustomed to testify their subjection by this ceremony, especially since they say that this practice is still observed in certain parts of the East. That it was no profane rite, which would detract anything from the glory of God, we infer from the fact that the name of God is interposed. It is true that the servant placed his hand under the thigh of Abraham, but he is adjured by God, the Creator of heaven and earth; and this is the sacred method of adjuration, whereby God is invoked as the witness and the judge; for this honor cannot be transferred to another without casting a reproach upon God. Moreover, we are taught, by the example of Abraham, that they do not sin who demand an oath for a lawful cause; for this is not recited among the faults of Abraham, but is recorded to his peculiar praise. It has already been shown that the affair was of the utmost importance, since it was undertaken in order that the covenant of God might be ratified among his posterity. He was therefore impelled, by just reasons, most anxiously to provide for the accomplishment of his object, by taking an oath of his servant: and beyond doubt, the disposition, and even the virtue of Isaac, were so conspicuous, that in addition to his riches, he had such endowments of mind and person, that many would earnestly desire affinity with him. His father, therefore, fears lest, after his own death, the inhabitants of the land should captivate Isaac by their allurements. Now, though Isaac has hitherto steadfastly resisted those allurements, the snares of which few young men escape, Abraham still fears lest, by shame and the dread of giving offense, he may be overcome. The holy man wished to anticipate these and similar dangers, when he bound his servant to fidelity, by interposing an oath; and it may be that some secret necessity also impelled him to take this course.
(2) Under my thigh. “A sign which Jacob also required of his son Joseph, (Genesis 47:29,) either to signify subjection, or for a further mystery of the covenant of circumcision, or rather of Christ the promised seed, who was to come out of Abraham’s loins or thigh.” — Ainsworth.