It is not uncommon for a believer to say "I will pray for you". Which lets God and others know that there is forgiveness in your heart. God prays for us too. He also has forgiveness in his heart. In so many stories in the Bible you see how disappointed God becomes. How angry he can get. All to give way to his huge heart, filled with grace and mercy. Above all forgiveness. When we tell another we will pray for them and it is done without condition or judgement. It sends an authentic sign to God.
For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God, not by works, so that no one can boast.