Psalms 86:5 - Albert Barnes' Notes on the Bible

For thou, Lord, art good ... - This is another reason why God should hear his prayer; and it is a reason which may be properly urged at all times, and by all classes of persons. It is founded on the benevolence of God; on the fullness of his mercy to all that invoke his name. We should call in vain on a God who was not merciful and ready to forgive; but in the divine character there is the most ample foundation for such an appeal. In his benevolence; in his readiness to forgive; in the plenitude of his mercy, God is all that a penitent sinner could wish him to be. For if such a sinner should endeavor to describe what he would desire to find in God as a ground of appeal in his prayers, he could not express his feelings in language more full and free than God has himself employed about his own readiness to pardon and save. The language of the Bible on this subject would express, better than any language which he could himself employ, what in those circumstances he would wish to find God to be.