Charles H. Spurgeon on Psalms 136:8

The sun to rule by day. We cannot be too specific in our praises; after mentioning great lights, we may sing of each of them, and yet not outwear our theme. The influences of the sun are too many for us to enumerate them all, but untold benefits come to all orders of beings by its light, warmth, and other operations. Whenever we sit in the sunshine, our gratitude should be kindled. The sun is a great ruler, and his government is pure beneficence, because by God's mercy it is moderated to our feebleness; let all who rule take lessons from the sun which rules to bless. By day we may well give thanks, for God gives cheer. The sun rules because God rules; it is not the sun which we should worship, like the Parsees; but the Creator of the sun, as he did who wrote this sacred song. For his mercy endureth for ever. Day unto day uttereth speech concerning the mercy of the Lord; every sunbeam is a mercy, for it falls on undeserving sinners who else would sit in doleful darkness, and find earth a hell. Milton puts it well:

"He, the golden tressed sun

Caused all day his course to run;

For his mercy shall endure

Ever faithful, ever sure."