Psalms 104:19

The appointed rule of the great lights is now the theme for praise. The moon is mentioned first, because in the Jewish day the night leads the way. He appointed the moon for seasons. By the waxing and waning of the moon the year is divided into months, and weeks, and by this means the exact dates of the holy days were arranged. Thus the lamp of night is made to be of service to man, and in fixing the period of religious assemblies (as it did among the Jews) it enters into connection with his noblest being. Never let us regard the moon's motions as the inevitable result of inanimate impersonal law, but as the appointment of our God. The sun knoweth his going down. In finely poetic imagery the sun is represented as knowing when to retire from sight, and sink below the horizon. He never loiters on his way, or pauses as if undecided when to descend; his appointed hour for going down, although it is constantly varying, he always keeps to a second. We need to be aroused in the morning, but he arises punctually, and though some require to watch the clock to know the hour of rest, he, without a timepiece to consult, hides himself in the western sky the instant the set time has come. For all this man should praise the Lord of the sun and moon, who has made these great lights to be our chronometers, and thus keeps our world in order, and suffers no confusion to distract us.

The appointed rule of the great lights is now the theme for praise. The moon is mentioned first, because in the Jewish day the night leads the way. He appointed the moon for seasons. By the waxing and waning of the moon the year is divided into months, and weeks, and by this means the exact dates of the holy days were arranged. Thus the lamp of night is made to be of service to man, and in fixing the period of religious assemblies (as it did among the Jews) it enters into connection with his noblest being.

He appointed the moon for seasons - The heathens thought that the sun and moon were gods, and worshipped them as such. The psalmist shows, 1. That they are creatures dependent on God for their being and continuance; and, 2. That they were made for the use of man. See what has been said on these luminaries in the notes on Gen 1:14-16 (note).

He appointed the moon for seasons - Gen 1:14-18. That is, The moon, as well as the sun, is appointed to divide time; to determine its progress; to indicate the return of festival occasions, or appointed times to be observed in any manner. It is, in fact, the foundation of the division of the year into “months,” and consequently the indication of all that is to be observed in the “months” of the year. But for this, there would be no natural divisions of time except those of day and night, and of the year. How great an advantage it is for the purpose of life, to have time broken up into brief intervals or periods which can be marked and remembered, both in our private life and in history, it is not necessary to say. God has been pleased to add to the natural divisions of time into days, and years, and months, an “artificial” division - the “fourth” part of the moon’s course - “a week,” indicated by the Sabbath, thus greatly facilitating the plans of life in regard to stated times or “seasons,” and especially in regard to religious observances. The idea in the passage before us is, that the whole arrangement is one of benevolence, promoting the comfort of man, and bringing the ideas of succession, variety, and beauty into the system. The sun knoweth his going down - As if conscious of what he is doing, he knows the exact time of setting, and never varies, but always obeys the divine command; never sets “before” his time - unexpectedly shortening the day, and leaving man in sudden darkness in the midst of his toil; and never lingers above the horizon “after” the moment has come for his setting, but withdraws at the exact time, enabling man to close his toil, and seek repose, and giving an opportunity for another class of creatures to come forth on the animated scene. […]