We've seen that whatever flows out in our life or through our mouths originates in our hearts. If the source is pure, that which comes out will be pure. If the source is corrupt, that which comes out will be corrupt. With this, we can compare the words of Hebrews 12:15-16:
"See to it that no one comes short of the grace of God; that no root of bitterness springing up causes trouble, and by it many be defiled; that there be no immoral or godless person like Esau, who sold his own birthright for a single meal." (NAS)
Esau was entitled to the birthright, but he sold it and lost it. We can have a birthright or a promise from God, but if we do not conduct ourselves rightly, we will lose our birthright and our inheritance, just like the ten spies who came with the negative report.
The reason why Esau acted like that is traced back to a root of bitterness in his heart. He was bitter against his brother Jacob. This root of bitterness in his heart brought forth bitter fruit in his life which corrupted his life and caused him to lose his birthright. (See Genesis 25:19-34.) Therefore, the root of the problem was in his heart.
The Scripture warns us that if there is a root of bitterness in the heart of any one of us, others may be defiled by it. The corrupt, negative use of the tongue is infectious. The ten spies came back with a negative report. They corrupted the whole nation. The whole nation was infected with that negative disease. That is one reason why God treats it so seriously. It is an infectious disease.
There are other examples of evil roots in our hearts that express themselves through our tongues and cause problems that rob us of the blessings that God desires us to have. We can have roots of resentment, unbelief, impurity, or pride. Whatever the nature of the root in our hearts, it will manifest itself in the way we speak. We may want to be gracious and kind, but a root of resentment will poison our words with a kind of resentful spirit. We will try to say nice things, but they will not come out right. We may claim to be believers, but a root of unbelief will cause us to do as the ten spies and add our "nevertheless" to God's promises. The same applies to impurity and pride.
Let me remind you of the story about the doctor in the desert checking his dysentery patients. The first question was, "Good morning, how are you?" But he did not really care much about the answer to that question. The second request was, "Show me your tongue." How would you respond if God said to you, "Show me your tongue"?
Dear Lord, please help me never to let any bitterness enter my heart. And I pray that You would show me and give me the grace to repent if there is any bitterness, resentment, unforgiveness, or other bitter roots in my heart right now. Thank You for Your atoning Blood and the power of Your Holy Spirit. Only in You do I have life. In Jesus' Name, Amen.