Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 4:1-20

“Or we may understand in a different way His speaking to the rest in parables, that seeing they might not perceive, and hearing, not understand. For God gives sight and understanding to men who seek for them, but the rest He blinds, lest it become a greater accusation against them, that though they understood, they did not choose to do what they ought. Wherefore it goes on, Lest at any time they should be, &c.”