Psalms 62:11-12 (ESV) 11 Once God has spoken; twice have I heard this: that power belongs to God, 12 and that to you, O Lord, belongs steadfast love (mercy in some translations). For you will render to a man according to his work.
“This looks rather like justice than mercy; but if we understand it to mean that God graciously rewards the poor, imperfect works of His people, we see in it a clear display of mercy. May it not also mean that according to the work He allots us is the strength which He renders to us? He is not a hard master, but metes out for us strength equal for our day. In either meaning we have the power and mercy blended, and have a double reason for waiting upon God.”
– Charles Spurgeon (Commentary on Psalms volume 1, pg. 255)