"It’s not what goes into your body that defiles you; you are defiled by what comes from your heart.”
It is so important that our hearts open and we let God transform them into His likeness. When our heart is involved in something our belief in that thing grows and we desire it more. When something comes into our heart that we care about we work harder to maintain it than we would something that just comes into our mind. This is why we are told to love God with all our mind, heart, soul and strength. If it was just one of these it wouldn't be a total surrender.
Look at what Jesus goes on to say about our hearts. Mark chapter 7 verses 21-23 says, "For from within, out of a person’s heart, come evil thoughts, sexual immorality, theft, murder, adultery, greed, wickedness, deceit, lustful desires, envy, slander, pride, and foolishness. All these vile things come from within; they are what defile you.” We have to guard our heart and mind as we grow so what comes out is not what our flesh thinks of but what God has filled it with. This is why it is important for us to read God's word and seek His will. I don't know about anyone else but my mind races and I can be on one thought one second and something else will pop in there totally different than what I was thinking about. My wife always says, how did you ask me that question from the conversation we were having? If I don't pray and read God's word to have that good in there my flash drives me and I just think of my desires.
My reading and believing in what I am reading has opened my mind and heart to think if His greatness so when I feel my mind going off in it's own direction I can bring it back to God's word. In my heart I believe that God's word is truth and all good for me to learn and follow just as it says in 2 Timothy 3:16 "All Scripture is inspired by God and is useful to teach us what is true and to make us realize what is wrong in our lives. It corrects us when we are wrong and teaches us to do what is right." This is what helps me grow and change from who I was to who I am, and I hope to continue maturing and changing from the inside out.
2 Timothy chapter 3 verse 17 goes on to say, "God uses it to prepare and equip his people to do every good work." It doesn't say every work we desire it says every good work, so I want to open my heart and let Him fill me and change me so what comes out of my mouth is good and inviting to people that hear me. Thank you Lord for giving me the tools and loving me, I desire your direction and wisdom so I can not be defiled by what comes out if my mouth. Amen