14 Then he called the crowd again and said to them, "Listen to me, all of you, and understand: 15 there is nothing outside a person that by going in can defile, but the things that come out are what defile." 16 

Matthew Henry's Commentary on Mark 7:14-16

Commentary on Mark 7:14-23

(Read Mark 7:14-23)

Our wicked thoughts and affections, words and actions, defile us, and these only. As a corrupt fountain sends forth corrupt streams, so does a corrupt heart send forth corrupt reasonings, corrupt appetites and passions, and all the wicked words and actions that come from them. A spiritual understanding of the law of God, and a sense of the evil of sin, will cause a man to seek for the grace of the Holy Spirit, to keep down the evil thoughts and affections that work within.