What does Psalm 51:15 mean?

David's sins had sealed his lips and kept him from offering genuine praise to God. However, David promised to declare God's praise if God would lift his guilt and forgive his transgressions. Perhaps he wrote Psalm 51 as a song he intended to sing to transgressors to teach them God's ways.

We Christians ought to sing praise to God for what He has done for us. He has forgiven our sins, given us a new life, a living hope, and a glorious inheritance (1 Peter 1:3–9). We ought to express the joy of our salvation in heartfelt praise to God. Psalm 40:2–3 can be our testimony: "He drew me up from the pit of destruction, out of the miry bog, and set my feet upon a rock, making my steps secure. He put a new song in my mouth, a song of praise to our God." Praise should be as important an aspect of our worship as any other.