Matthew 15:18

Clement of Alexandria The Instructor Book II

From filthy speaking we ourselves must entirely abstain, and stop the mouths of those who practise it by stern looks and averting the face, and by what we call making a mock of one: often also by a harsher mode of speech. "For what proceedeth out of the mouth," He says, "defileth a man,"[120]

Origen Commentary on Matthew Book XI

Next to this let us see how the things which proceed out and defile the man do not defile the man because of their proceeding out of the mouth, but have the cause of their defilement in the heart, when there come forth out of it, before those things which proceed through the mouth, evil thoughts, of which the species are-murders, adulteries, fornications, thefts, false witness. railings.[143]