Joshua 22:27-28, 34

but to be a witness between us and you, and between our generations after us, that we do perform the service of the LORD in his presence with our burnt offerings and sacrifices and peace offerings, so your children will not say to our children in time to come, “You have no portion in the LORD.”’ And we thought, ‘If this should be said to us or to our descendants in time to come, we should say, “Behold, the copy of the altar of the LORD, which our fathers made, not for burnt offerings, nor for sacrifice, but to be a witness between us and you.”’

The people of Reuben and the people of Gad called the altar Witness, “For,” they said, “it is a witness between us that the LORD is God.”