What does 2 Kings 5:15 mean?

He and his whole group went back to Elisha. He stood in front of him and said, 'Now I know there's no God anywhere except in Israel. Please, take a gift from me.' 2 Kings 5:15 - Modern Text Bible

(Naaman returns, grateful and convinced that Israel's God is the real one. He tries to give Elisha a gift in thanks.)