What Goes In, Must Come Out

20And He was saying, “That which proceeds out of the man, that is what defiles the man. 21“For from within, out of the heart of men, proceed… Mark 7:20-21a NASB

Jesus is addressing the fact, that people thought that certain foods, drinks, and dirt from this world could corrupt us and remove us from our right standing with God. Jesus is pointing out the fact that who we are is not simply flesh and bones, but who we are is immaterial. Our heart and soul are immaterial things that make us who we are, so, material things coming into us from the outside cannot defile us at our core. But understand that Jesus is not saying that nothing that comes into us has no effect. How can I say this? Because of the parable of the sower of the seeds. The difference is the seed in the parable of the sower of the seeds represents something spiritual. What Jesus is addressing here in Mark 7, is solely a material argument. In the parable of the sower of the seeds, the individual heard the word (it entered the mind) and then it either immediately got plucked away, or it went into the heart to take root, grow, and eventually produce fruit. The same principle of the sower of the seed happens with the world's system as well. They plant a seed of "truth" into the mind of man with the desire that it would grow and produce their fruit (Galatians 5:19-26).
So, how do the things that proceed from the heart of man, get there in the first place? From within and from without. As sinful humans, we do not need any help to sin. We have the roots of sin in our hearts already, that flow out in evil ways. Jeremiah 17:9,10 says: “The heart is more deceitful than all else And is desperately sick; Who can understand it? 10“I, the LORD, search the heart, I test the mind, Even to give to each man according to his ways, According to the results of his deeds. These verses in Jeremiah show us that we have a serious heart problem as humans that needs to be remedied. We haven't made a few mistakes, the core of our being is corrupted to the point of being more deceitful than anything else. This is why we need a completely new heart, which comes to us through being born-again through the Holy Spirit (Ezekiel 36:26-27) 
Although we don't need help to sin, we are certainly receiving it! On a daily basis, we are being fed evil thoughts and ideas from this world that is under the power of Satan (1 John 5:19). This is being done with the hope that these small seeds of thought will grow into bountiful trees with evil fruit. This is why we have been told in Proverbs 4:23, Watch over your heart with all diligence, For from it flow the springs of life. What scripture is telling us here, is to set a guard over our hearts from outside influences that are threatening to get in. For from our heart flows the springs of life. The nature of those springs that flow from our hearts will be determined by the roots. What we allow into our hearts is what will develop the “evil thoughts”, which is the beginning of the rest of the sins that Jesus says flows from the heart of man. 
As those who have placed their trust in Christ, and have been given a new heart and a new spirit, we are not immune from corruption that threatens to get inside of us. We must be diligent in putting to death the deeds of the flesh, and vigilant against the schemes of our enemy. Do not let the serpent from the garden, plant his seeds of doubts and lies into your mind; you are a son to the King, walk in that authority today. 

Questions to Consider:

1. What are some practical ways that we can, or that you have found successful in "guarding our hearts" from outside influences? 

2. Do you know someone that has not yet been born-again by putting their faith in Christ? Would you take a moment and intercede on their behalf?