So the servant placed his hand under the thigh of his master Abraham and swore an oath to him concerning this matter.
Three things we may observe here concerning Abraham: - I. The care he took of a good son, to get him married, well married. It was high time to think of it now, for Isaac was about forty years old, and it had been customary with his ancestors to marry at thirty, or sooner, Gen 11:14, Gen 11:18, Gen 11:22, Gen 11:24.
Commenting on Genesis 24:1-9
And the servant put his hand under the thigh of Abraham his master,.... Or "then" or "therefore the servant", &c. (n) being satisfied of the nature and extent of his oath, and thoroughly understanding how he was to act upon it, readily took it by using this rite; see Gill on Gen 24:2, and sware to him concerning that matter; of taking a wife to...
Put his hand under the thigh of Abraham - This form of swearing has greatly puzzled the commentators; but it is useless to detail opinions which I neither believe myself, nor would wish my readers to credit. I believe the true sense is given in the Targum of Jonathan ben Uzziel, and that called the Jerusalem Targum.