“It is not what goes
Into the mouth
That defiles a person.
But what comes out
Of the mouth
That defiles a person.”
οὐ τὸ εἰσερχόμενον εἰς τὸ στόμα κοινοῖ τὸν ἄνθρωπον, ἀλλὰ τὸ ἐκπορευόμενον ἐκ τοῦ στόματος τοῦτο κοινοῖ τὸν ἄνθρωπον.
There is something similar to this in Mark, chapter 7:15. Jesus, via Matthew, went back to the problem of impurity, unclean or defiled people. Thus, spiritual purity was more important that physical purity. It is not what you put into or what enters into your mouth (οὐ τὸ εἰσερχόμενον εἰς τὸ στόμα), such as unclean food, that pollutes or defiles a man or a person (κοινοῖ τὸν ἄνθρωπον). Rather, what comes out of your mouth (ἀλλὰ τὸ ἐκπορευόμενον ἐκ τοῦ στόματος τοῦτο), such as words, that defile, pollute or make a man or person unclean (κοινοῖ τὸν ἄνθρωπον). It is not what you put into your mouth that makes you unclean, it is what comes out of your mouth that makes you unclean or defiled.
Eugene Finnegan Bible Project 