Genesis 24:5 (KJV)

And Abraham was old, and well stricken in age: and the LORD had blessed Abraham in all things.

And Abraham said unto his eldest servant of his house, that ruled over all that he had, Put, I pray thee, thy hand under my thigh:

And I will make thee swear by the LORD, the God of heaven, and the God of the earth, that thou shalt not take a wife unto my son of the daughters of the Canaanites, among whom I dwell:

But thou shalt go unto my country, and to my kindred, and take a wife unto my son Isaac.

And Abraham said unto him, Beware thou that thou bring not my son thither again.

The LORD God of heaven, which took me from my father's house, and from the land of my kindred, and which spake unto me, and that sware unto me, saying, Unto thy seed will I give this land; he shall send his angel before thee, and thou shalt take a wife unto my son from thence.

And if the woman will not be willing to follow thee, then thou shalt be clear from this my oath: only bring not my son thither again.

And the servant put his hand under the thigh of Abraham his master, and sware to him concerning that matter.

And the servant took ten camels of the camels of his master, and departed; for all the goods of his master were in his hand: and he arose, and went to Mesopotamia, unto the city of Nahor.