From the New Testament, we read about the teaching of Jesus on holiness:
"Are you so dull?" he (Jesus) asked, "Don't you see that nothing that enters a man from the outside can make him unclean? For it doesn't go into his heart but into his stomach, and then out of his body." He went on: "What comes out of a man is what makes him 'unclean.' For from within, out of men's hearts come evil thoughts, sexual immorality, theft, murder, adultery, greed, malice, deceit, lewdness, envy, slander, arrogance, and folly. All these evils come from inside and make a man 'unclean'."
Mark 7:18-23
I will come up with more later, but I am past my bedtime now.