“He said, ‘What comes out of a person defiles him. For from within, out of the human heart, come evil ideas, sexual immorality, theft, murder, adultery, greed, evil, deceit, debauchery, envy, slander, pride, and folly. All these evils come from within and defile a person.’”
Jewish tradition concerned itself with what defiled and made one impure. Jesus went to the heart of the matter. Defilement starts from within, in the mind.
Control of mind starts with Scripture. Reading, meditating, and praying over the Bible purifies and strengthens. God renews the mind, Rom 12.1-2, and thus the whole person.