Catena Aurea on Mark 4:26–29: Pseudo-Chrysostom

Or else He says, “He knoweth not,” that He may shew the free-will of those who receive the word, for He commits a work to our will, and does not work the whole Himself alone, lest the good should seem involuntary. For the earth brings forth fruits of its own accord, that is, she is brought to bear fruit without being compelled by a necessity contrary to her will. “First the blade.”