Mark 7:21–23 (ESV) … “For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness. All these evil things come from within, and they defile a person.”
In Mark 7, we find a list or a catalog of sinful horrors. Furthermore, it is frightening to think that we carry all of them around in our hearts. Truly, as the prophet said, “The heart is deceitful above all things, and desperately wicked” (Jer. 17:9).
What we must remember, is that the Lord looks into everyone’s heart. Everywhere He looks, He sees these dreadful things. We have only to look within our own hearts to see them for ourselves.
Restraints are imposed upon us by society, family, friends, conscience, the church, and the Holy Spirit, but all of these things are there just the same. Only God’s grace keeps us from expressing them. No wonder Jesus told Nicodemus that we need to be born again (John 3:3).
What might need confessing today? What horror within needs the touch of God’s grace and holiness? That is the climax of the argument. This is real uncleanness, the uncleanness that destroys, and not mere ritual uncleanness.
In this passage, the Lord went to the heart of the matter. And how terribly defiling these things are! These are the things that wreck homes and ruin lives and start wars and spread disease. These are the things that, in their appalling and incalculable sum, were to be placed upon the Lord Jesus at Calvary and for which He would have to die. 
 Phillips, J. (2009). Exploring the Gospel of Mark: An Expository Commentary (Mk 7:21–22). Kregel Publications; WORDsearch Corp.