Charles H. Spurgeon on Psalms 86:5

For thou, Lord, art good, and ready to forgive. Good at giving and forgiving; supplying us with his good, and removing our evil. Here was the great reason why the Psalmist looked to the Lord alone for his joy, because every joy creating attribute is to be found in perfection in Jehovah alone. Some men who would be considered good are so self exultingly indignant at the injuries done them by others, that they cannot forgive; but we may rest assured that the better a being is, the more willing he is to forgive, and the best and highest of all is ever ready to blot out the transgressions of his creatures. And plenteous in mercy unto all them that call upon thee. God does not dispense his mercy from a slender store which perchance may be so impoverished as to give out altogether, but out of a cornucopiae he pours forth the infinite riches of his mercy: his goodness flows forth in abounding streams towards those who pray and in adoring worship make mention of his name. David seems to have stood in the cleft of the rock with Moses, and to have heard the name of the Lord proclaimed even as the great lawgiver did, for in two places in this psalm he almost quotes verbatim the passage in Ex 34:6 —"The Lord God, merciful and gracious, longsuffering, and abundant in goodness and truth."