The Hands: Placed Under the Thigh of a Person to Whom an Oath Was Made
Source: TTT
Genesis 24:2, 3
So Abraham instructed the chief servant of his household, who managed all he owned, “Place your hand under my thigh, / and I will have you swear by the LORD, the God of heaven and the God of earth, that you will not take a wife for my son from the daughters of the Canaanites among whom I am dwelling,
Genesis 47:29, 31
When the time drew near for Israel to die, he called his son Joseph and said to him, “If I have found favor in your eyes, put your hand under my thigh and promise to show me kindness and faithfulness. Do not bury me in Egypt, / “Swear to me,” Jacob said. So Joseph swore to him, and Israel bowed in worship at the head of his bed.