This is the end of the question that begins with the words "Do you not see" in verse 18. Jesus uses this question to teach his disciples something they should already know. It can be expressed as a statement. "You should already understand that whatever enters into a person from outside cannot defile him, because it cannot go into his heart, but it goes into his stomach and then passes out into the latrine." (See: [[rc://en/ta/man/jit/figs-rquestion]])
Here "heart" is a metonym for a person's inner being or mind. Here Jesus means that food does not affect a person's character. Alternate translation: "it cannot go into his inner being" or "it cannot go into his mind" (See: [[rc://en/ta/man/jit/figs-metonymy]])
It may be helpful to explain clearly what this phrase means. Alternate translation: "all foods clean, meaning that people can eat any food without God considering the eater defiled" (See: [[rc://en/ta/man/jit/figs-explicit]])