Note 19 at Joh 5:39: Jesus had already said that the witness of His Father was His greatest testimony of who He was. This could be done through physical manifestations (see note 18 at Joh 5:32) or, as He was stating here, the Scriptures. Not everyone will hear God speak in an audible voice, but everyone can hear His testimony of Jesus through the Scriptures. Moses and all the Old Testament prophets spoke of the coming of Jesus (Joh 5:46 and Lu 24:27, special note of Ps 45:6-7 with Heb 1:8-9), and Peter said the written Word of God was a more sure word of prophecy than the audible voice of God (2Pe 1:17-20, compare with Lu 16:31).