Create in me a pure heart, O God (Psalm 51:10a NIV).
This is a sincere prayer coming from the heart of a repentant man. He is desperate in his prayer. He knows that God alone can create in him a pure heart. When these conditions meet together, God can create in you too a pure heart.
To pray to God to create within you a pure heart you first of all need to see the great filth of your sin. This realization does not come easily. But there comes moments in life when God confronts you and gives you grace to see how much sin has dirtied your heart. Some people continue to ignore such moments of grace. Some others repent and pray to God to create in them a pure heart. You too can join them in this prayer for this moment is a moment of such grace.
Again, you need to realize that the grip of sin in your life is powerful. It will not release its victims easily. A magical wish kind of prayer will not create in you the miracle of a pure heart. But desperate longing and crying out to God in sorrow and repentance will do it. That longing comes only when God gives you insight into how terrible it is to live in sin and also show you a glimpse of the radiant beauty of a pure heart. When such a moment of grace occurs in your life, cry out with all your heart to God to create within you a pure heart.
But there is something more to it. Even though it is true that God creates within you a pure heart; it is also true that you have a responsibility in keeping it pure. There is no automatic life-long guarantee of purity. It is here that many people are mistaken. They think that a one-time encounter with God will always keep them pure. It is not so. Instead, purity of heart can only be maintained by a moment by moment dependence on God. It also requires a constant guard against sin. Realizing this truth, David continued his prayer, saying, “and renew a steadfast spirit within me.” He not only wanted a pure heart but also a divine enabling to continue to live with a pure heart!