Genesis 21:25-31

When Abraham reproved Abimelech about a well of water that Abimelech’s servants had seized, Abimelech said, “I do not know who has done this thing; you did not tell me, and I have not heard of it until today.” So Abraham took sheep and oxen and gave them to Abimelech, and the two men made a covenant. Abraham set seven ewe lambs of the flock apart. And Abimelech said to Abraham, “What is the meaning of these seven ewe lambs that you have set apart?” He said, “These seven ewe lambs you will take from my hand, that this may be a witness for me that I dug this well.” Therefore that place was called Beersheba, because there both of them swore an oath.