a witness.

Genesis 31:44-48, 52
Come now, let us make a covenant, you and I, and let it serve as a witness between you and me." . . .

Joshua 22:27, 28
Rather, let it be a witness between us and you and the generations to come, that we will worship the LORD in His presence with our burnt offerings, sacrifices, and peace offerings.' Then in the future, your descendants cannot say to ours, 'You have no share in the LORD!' . . .

Joshua 24:27
And Joshua said to all the people, "You see this stone. It will be a witness against us, for it has heard all the words the LORD has spoken to us, and it will be a witness against you if you ever deny your God."