'You are Witnesses' in the Bible

Boaz said to the elders, and to all the people, "You are witnesses this day, that I have bought all that was Elimelech's, and all that was Chilion's and Mahlon's, from the hand of Naomi.

Moreover Ruth the Moabitess, the wife of Mahlon, I have purchased to be my wife, to raise up the name of the dead on his inheritance, that the name of the dead not be cut off from among his brothers, and from the gate of his place. You are witnesses this day."