Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 4:30-34

“For since the multitude was unlearned, he instructs them from objects of food and familiar names, and for this reason he adds, But without a parable spake he not unto them, that is, in order that they might be induced to approach and to ask Him. It goes on; And when they were alone, he expounded all things to his disciples, that is, all things about which they were ignorant and asked Him, not simply all, whether obscure or not.”