Say there is a reward for the righteous.Psalm 58:11
The Lord tells us in this Scripture that we must always come to this conclusion: When you see things in such confusion that all order is turned upside down and God favors the wicked and hates the good, or that only chance rules, that God is asleep in heaven, that he no longer governs the affairs of this world, you must continue to be convinced that the righteous will reap the fruit of their labors.
So it is true there can be no worse temptation than to think we waste our labor when we serve God, bless his name, and submit to him, but we must be persuaded that God does not intend to disappoint those who honor and serve him.
If we do not have that assurance, we cannot ever have the least desire to devote ourselves to God. If we think that God turns his back on us, that he mocks us when we labor here below, that he closes his eyes, and that we waste our time living with great care, who among us can apply himself to well-doing?
Therefore, because those who serve God and draw nearest to him have that conviction, he rewards those who fear him. We see that the worst and deadliest temptation that Satan can place before us is to make us think we waste our time when we pray to God and have recourse to him. All the more must we be vigilant against that temptation, seeing that it is so dangerous and destructive.
[John Calvin, Sermons on Job, Vol 1 pp 105-6, Banner of Truth Trust]