John Chrysostom — as excerpted in the Catena Aurea on Matthew 13:24-30

“In what follows He more particularly draws the picture of an heretic, in the words, When the blade grew, and put forth fruit, then appeared the tares also. For heretics at first keep themselves in the shade; but when they have had long license, and when men have held communication with them in discourse, then they pour forth their venom.”