'You are Witnesses' in the Bible

Then Boaz said to the responsible men and to all the people, You are witnesses today that I have taken at a price from Naomi all the property which was Elimelech's, and everything which was Chilion's and Mahlon's.

And, further, I have taken Ruth, the Moabitess, who was the wife of Mahlon, to be my wife, to keep the name of the dead man living in his heritage, so that his name may not be cut off from among his countrymen, and from the memory of his town: you are witnesses this day.