Charles H. Spurgeon on Psalms 136:7

Great lights. The luminaries of heaven are unspeakable blessings to the children of men. The sun, in the greatness of his strength, measures their day, and exerts an influence over animal and vegetable life, which surrounds them with innumerable comforts; and the moon and stars walking forth in their brightness, give direction to them amidst the sable hours of night, and both by land and sea proclaim the wisdom, and benignity, and gracious arrangement of the adorable Creator. By these luminaries, day and night, heat and cold, summer and winter are continually regulated: so that God's covenant with the earth is maintained through their medium. How truly, then, may we exclaim, "His mercy endureth for ever!" —John Morison.