Albert Barnes on John 8:47

He that is of God. He that loves, fears, and honours God.

Heareth God's words. Listens to, or attends to the doctrines or commandments of God, as a child who loves his parent will regard and obey his commandments. This is an evidence of true piety. A willingness to receive all that God teaches us, and to obey all his commandments, is an undoubted proof that we are his friends, Jn 14:21, 1Jn 2:4, 3:24. As the Jews did not show a readiness to obey the commands of God, it proved that they were not of him, and to this was owing their rejection of the Lord Jesus.