# because ... latrine?

"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."

# it cannot go into his heart

"it cannot go into his inner being" or "it cannot go into his mind"

# all foods clean

"all foods clean, meaning that people can eat any food without God considering the eater defiled"