This verse is in the form of what is technically known as an antithetic parallelism, in which the two halves of the verse each convey essentially the same message but in contrasting ways: what goes into contrasts with what comes out of.

What goes into the mouth obviously refers to food and drink, and some translators have felt it necessary to say that: “the food and drink a person puts in his mouth.” However, it is usually sufficient to say “what a person puts in his mouth.”

Defiles (so also Moffatt, Barclay) is rendered “makes … unclean” by New Jerusalem Bible and New International Version: Good News Translation has “makes … ritually unclean.” According to Jewish teaching a person must be “clean” when he approaches God in worship, and “cleanliness” was defined both in terms of moral deeds and ritual actions. Anyone who had committed a sinful deed or had failed to comply with ritual regulations was considered “unclean” or “defiled” and was therefore not permitted to worship God. One may translate “that makes a person unfit to worship God,” “… a person unacceptable to God,” or “… a person’s worship unacceptable to God.” Translators who want to keep the image of “unclean” can say “that makes a person unclean in God’s sight” or “… unclean before God.” In the last half of the verse, Good News Translation replaces “makes … ritually unclean” with “makes … unclean” because the nature of the uncleanliness is clearly defined by Good News Bible in the first part of the verse.

A man means “a person,” although it is true that in the Jewish setting men were the only ones who actively participated in the worship services. Most translations will have “a person” or “someone,” however.

What comes out of the mouth clearly does not refer to food, and translators who used “food” in the first part of the verse will have to make sure the readers don’t think this phrase refers to food too. It is best not to be specific about what comes out of the mouth, but “the words a person speaks” is sometimes necessary.

Good News Translation has followed the structure of the text, the antithetic parallelism discussed above. There are languages where a better structure will be “It is not what a person puts in his mouth that make him unfit to worship God; the things that make him unclean like that are the things that come out of his mouth,” or even “A man does not become unclean in God’s sight because of something he puts in his mouth. Rather, the things that make him unclean are what come out of his mouth.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .