To shew that the LORD is upright: he is my rock, and there is no unrighteousness in him. To show that the Lord is upright - Such persons show how faithful God is to his promises, how true to his word, how kind to them who trust in him. He is the Rock, the Fountain, whence all good comes.
There is no unrighteousness in him - He does nothing evil, nothing unwise, nothing unkind. He is both just and merciful.
Commentary on the Bible, by Adam Clarke [1831].