If I had cherished sin in my heart, the Lord would not have listened; but God has surely listened and heard my voice in prayer. Praise be to God, who has not rejected my prayer or withheld his love from me” (Psalm 66:18,19,20 NIV)!
The psalmist is here calling people to come and listen to what God has done for him. He says that he cried out to God and he was heard when he praised God. Then he focusses our attention to a condition that might have stopped his prayer from being heard. He points out the fact that if he had cherished sin in his heart, God would not have heard his prayer.
What is meant by cherishing sin in one’s heart? It means holding sin dear to us. It means loving sin so much that you find it very difficult to let go off it completely. Such a condition, the psalmist says, can prevent God from listening to your prayer.
Why is this so? This is so because our God is a holy God. And prayer is our channel of communication with God. If sin has found a strong lodging in our heart, our prayers would be corrupted by it. And a sin-stained prayer cannot be heard by God because He is a holy God.
Sin in our heart can block prayer because it is like a lot of interruptions on the telephone line that makes the voice unintelligible. It can be compared to a lot of impurities that get collected in a pipe so that the smooth flow of water is curbed. It is also like a strong acid that gradually corrodes the vessel that holds it. It is similar to cancer that spreads and destroys. So, if sin can be removed from our hearts, God will not reject our prayer or withhold His love!