John Chrysostom
Catena Aurea · Matthäusevangelium 7
Beware of false prophets, which come to you in sheep’s clothing, but inwardly they are ravening wolves. Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit. A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit. Every tree that bringeth not forth good fruit is hewn down, and cast into the fire. Wherefore by their fruits ye shall know them.
And a hypocrite is easily discerned; for the way they are commanded to walk is 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?