After I turned forty, the doctor told me to regard food as medicine. He explained that in previous years, what I ate did not affect me as much as it does now that I have passed forty. I need to be careful what I eat and how much I eat, because it now has a deeper and longer lasting effect on me.
I am reminded how careful I need to be about what I put in my body, and even more so what I put into my mind through my ears and eyes. Temptations sometimes are so subtle at the outset that they seem harmless. Pride wants to blow it off. But humility leads me to confess that I am just as susceptible as anyone else. There was a time I could have gotten entangled in an extra-marital affair. In fact, I was well on the road heading that direction before I began to realize what was happening. It was so innocent at first.
There is a reason the Bible says, "Watch over your heart with all diligence, For from it flow the springs of life" (Prov 4:23 NASB). It does not take much to pollute that spring. If it does become polluted, it affect not only yourself, but all those around you as well, especially those closest to you. That pollution starts in the mind and heart, long before it expresses itself in actions.
But it occurs to me that pollution of the heart often works in reverse. I am reminded of when Jesus said, "What goes into someone’s mouth does not defile them, but what comes out of their mouth, that is what defiles them” (Mt 15:11). Jesus went out to describe how things like evil thoughts, slander, immorality, and other such things come out of the mouth by way of the heart, and this is what defiles them.
It may seem strange that something coming out rather than something going in can defile a person. However, experience demonstrates this truth. Think about those times you think about giving someone a piece of your mind. It would feel so much better to let it all out and just let them have it. So you go through with it and hold nothing back. This rarely if ever makes those thoughts go away. If anything, it entrenches them deeper into your heart. Contrary to popular wisdom, getting it all out is not a solution to negative thoughts and feelings.
It would seem that the solution is just to hold it all back. If it doesn't pass through your lips, then it can't defile you. However, the Bible goes much further than just zipping your lips. Romans 12:14 tell us to "Bless those who persecute you; bless and do not curse." However, I like the passage from Ephesians 5:18-21 because of the contrast it gives to Matthew 15:11.
"… be filled with the Spirit, speaking to one another in psalms and hymns and spiritual songs, singing and making melody with your heart to the Lord; always giving thanks for all things in the name of our Lord Jesus Christ to God, even the Father" (Eph 5:18-21 NASB).
When are you filled with the Spirit? It is when you are "speaking" to one another in psalms, hymns, and spiritual songs, and giving thanks. Being filled with the Spirit involves what comes out of our mouths. It increases the fruit of the Spirit, which includes love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control.
If I curse, swear, belittle, gossip, lie, or say anything else contrary to the Spirit, my heart becomes defiled. However, if I bless rather than curse, and if I encourage rather than discourage, and if I give thanks rather than complain, then I am being filled with the Spirit.
A good way to maintain the health of my heart is to watch what comes out of my mouth. What comes out of my mouth will either defile my heart, or fill me with the Spirit.