Theophylact of Ohrid — as excerpted in the Catena Aurea on John 1:6-8

“Though some however might not believe, he is not accountable for them. When a man shuts himself up in a dark room, so as to receive no light from the sun’s rays, he is the cause of the deprivation, not the sun. In like manner John was sent, that all men might believe; but if no such result followed, he is not the cause of the failure.”