Genesis 24:2-3. Abraham said unto his eldest servant... Put, I pray thee, thy hand under my thigh, and... swear.
1. The most intelligent and faithful servant in the household was appointed overseer of the others. The word “eldest” is not of necessity expressive of age, but of authority. This was the head servant, chief of all the rest, though some of them may have been over others. In a similar way we use the word “elder” in an official sense, even when applied to young men. Such head-servants or stewards may still be seen portrayed on Egyptian tombs, with their secretaries, implements of writing, stewards’ account books, and articles for domestic use. This was the position which Joseph filled (Gen. 39:4).
2. The mode of swearing here spoken of seems to have been peculiar to the patriarchs. Jacob required Joseph thus to swear to him (Gen. 47:29). Various conjectures have been made as to the precise position of the hand or hands in taking this oath, for which, as well as for the supposed significance of the oath, commentators may be consulted.