He said to them, Yahweh is witness against you, and his anointed is witness this day, that you have not found anything in my hand. They said, He is witness.
In other words, he is declaring his innocency before the people. "Look, I didn't take from you at all. I didn't take from you your oxen, your donkeys. I didn't accept bribes. I've not oppressed you. If anyone feels that I've oppressed you, anyone feels I've defrauded, step forward, and I will pay." Really Samuel did have a very beautiful and remarkable career as the judge of Israel. Extremely outstanding person.