John Calvin Commentary Psalms 136:7

"To him that made great lights; For his lovingkindness [endureth] for ever:" — Psalms 136:7 (ASV)

Who made the great lights, etc. — Moses calls the sun and moon the two great lights, and there is little doubt that the Psalmist here borrows the same phraseology. What is immediately added about the stars is, as it were, accessory to the others. It is true, that other planets are larger than the moon, but it is mentioned as second in order on account of its visible effects.

The Holy Spirit had no intention to teach astronomy. In offering instruction intended for the simplest and most uneducated people, He, through Moses and the other Prophets, used popular language. He did this so that no one might take refuge behind the pretext of obscurity, as people sometimes readily pretend an inability to understand when anything profound or difficult to grasp is presented to them. Accordingly, since Saturn, although bigger than the moon, does not appear so to the eye due to its greater distance, the Holy Spirit would rather speak childishly than unintelligibly to the humble and unlearned.

The same observation can be made about what the Psalmist adds regarding God having assigned the sun and moon their respective roles, making the one to rule the day, and the other to rule the night. We are not to understand from this that they exercise any actual government; rather, God’s administrative power is very manifest in this distribution. The sun, by illuminating the earth during the day, and the moon and stars by night, may be said to offer reverential homage to God.