Genesis 24:2-4

Abraham said to his servant [Eliezer of Damascus], the oldest of his household, who had charge over all that Abraham owned, “Please, put your hand under my thigh [as is customary for affirming a solemn oath], [Gen 15:2] and I will make 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 live, but you will [instead] go to my [former] country (Mesopotamia) and to my relatives, and take a wife for my son Isaac [the heir of the covenant promise].”