Genesis 24:1-10 ESV
Now Abraham was old, well advanced in years. And the LORD had blessed Abraham in all things. And Abraham said to his servant, the oldest of his household, who had charge of all that he had, “Put your hand under my thigh, that I may make you swear by the LORD, the God of heaven and God of the earth, that you will not take a wife for my son from the daughters of the Canaanites, among whom I dwell, but will go to my country and to my kindred, and take a wife for my son Isaac.” The servant said to him, “Perhaps the woman may not be willing to follow me to this land. Must I then take your son back to the land from which you came?” Abraham said to him, “See to it that you do not take my son back there. The LORD, the God of heaven, who took me from my father’s house and from the land of my kindred, and who spoke to me and swore to me, ‘To your offspring I will give this land,’ he will send his angel before you, and you shall take a wife for my son from there. But if the woman is not willing to follow you, then you will be free from this oath of mine; only you must not take my son back there.” So the servant put his hand under the thigh of Abraham his master and swore to him concerning this matter.
Then the servant took ten of his master’s camels and departed, taking all sorts of choice gifts from his master; and he arose and went to Mesopotamia to the city of Nahor.
ESV: English Standard Version 2016