Genesis 24:1-3

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: