Genesis 24:9 in the World English Bible
The servant put his hand under the thigh of Abraham his master, and swore to him concerning this matter.
Context
8 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.
9 And the servant put his hand under the thigh of Abraham his master, and sware to him concerning that matter.
10 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.