Having taught that the gate is strait, because there are many that pervert the way that leads to it, He proceeds, “Take heed of false prophets.” In the which that they might be the more careful, He reminds them of the things that were done among their fathers, calling them “false prophets;” for even in that day the like things fell out.
What is written below that “the Law and the Prophets were until John,” .
Yet He may seem here to have aimed under the title of “false prophets,” not so much at the heretic, as at those who, while their life is corrupt, yet wear an outward face of virtuousness; whence it is said, “By their fruits ye shall know them.” For among heretics it is possible many times to find a good life, but among those I have named never.
And the hypocrite is easily discerned; for the way they are commanded to walkis a hard way, and the hypocrite is loth to toil. And that you may not say that you are unable to find out them that are such, He again enforces what He had said by example from men, saying, “Do men gather grapes of thorns, or figs of thistles?”.
But that none should say, An evil tree brings forth indeed evil fruit, but it brings forth also good, and so it becomes hard to discern, as it has a two-fold produce; on this account He adds, “A good tree cannot bring forth evil fruit, neither can an evil tree bring forth good fruit.”.
He had not enjoined them to punish the false prophets, and therefore shows them the terrors of that punishment that is of God, saying, “Every tree thatbringeth not forth good fruit shall be hewn down, and cast into the fire. "In these words He seems to aim also at the Jews, and thus calls to mind the word of John the Baptist, denouncing punishment against them in the very same words. For he had thus spoken to the Jews, warning them of the axe impending, the tree that should be cut down, and the fire that could not be extinguished.
