Genesis 26:31-33

31Early the next morning, they each took a solemn oath not to interfere with each other. Then Isaac sent them home again, and they left him in peace.

32That very day Isaac’s servants came and told him about a new well they had dug. “We’ve found water!” they exclaimed.

33So Isaac named the well Shibah (which means “oath”). And to this day the town that grew up there is called Beersheba (which means “well of the oath”).