Psalms 33:22

Let thy mercy, O Lord, be upon us
That is, an application of it in its effects: it is a prayer for a communication of grace and mercy to help in a time of need; and for a discovery of pardoning grace and mercy; and it is a prayer of faith; for the mercy of the Lord is upon his people in great plenty, and it continues; and they have reason to believe it ever will, ( Psalms 103:17 ) ;

according as we hope in thee;
not according to any merits of theirs, but according to the measure of grace, of the grace of hope which God had bestowed on them, and encouraged them to exercise on him, in expectation of finding grace and mercy with him.