Alcuin of York — as excerpted in the Catena Aurea on John 5:31-40

“For it is not by the carnal ear, but by the spiritual understanding, through the grace of the Holy Spirit, that God is heard. And they did not hear the spiritual voice, because they did not love or obey Him, nor saw they His shape; inasmuch as that is not to be seen by the outward eye, but by faith and love.”