Genesis 21:26 (KJV)

And he dwelt in the wilderness of Paran: and his mother took him a wife out of the land of Egypt.

And it came to pass at that time, that Abimelech and Phichol the chief captain of his host spake unto Abraham, saying, God is with thee in all that thou doest:

Now therefore swear unto me here by God that thou wilt not deal falsely with me, nor with my son, nor with my son's son: but according to the kindness that I have done unto thee, thou shalt do unto me, and to the land wherein thou hast sojourned.

And Abraham said, I will swear.

And Abraham reproved Abimelech because of a well of water, which Abimelech's servants had violently taken away.

And Abraham took sheep and oxen, and gave them unto Abimelech; and both of them made a covenant.

And Abraham set seven ewe lambs of the flock by themselves.

And Abimelech said unto Abraham, What mean these seven ewe lambs which thou hast set by themselves?

And he said, For these seven ewe lambs shalt thou take of my hand, that they may be a witness unto me, that I have digged this well.

Wherefore he called that place Beersheba; because there they sware both of them.