In Samaria was a man named Simon. Before being converted Simon was a magician. As a believer he was amazed by the works of the apostles who performed miracles via the power of the Holy Spirit. When Simon saw that the giving of the Spirit was obtained through the laying on of hands, he sought to pay the apostles so that they might lay hands on him and give him the Holy Spirit.
Peter responded with harsh rebuke even to the point of commanding Simon to repent of the intent of his heart. Simon's reasoning evaded the significance of the cross. For the Holy Spirit to be given is for God to be on the move. And we know God does not move nor can he be manipulated according to the worthless pennies of this world.
Herein Peter tells Simon to repent! Even if the intent of his heart was exercised in ignorance, repentance is still require.
At times we assume that sin should only be repented of if we act upon it or dwell upon the thoughts or desires of it. However, how often have we been convicted and we right it off as being 'not a big deal'? As God brings sinful motives to mind it is our responsibility to make much of that grace by turning to Christ with those heart intentions so that we might find forgiveness and cleansing from those sins which often stifle our relationship with God.
Run to Christ to be freed even from the intentions of your hearts.