Ps 103:19

“Consider that the sun, the moon and the stars, the lights of the sky which, though they shine with brilliant splendor, are yet creatures, and, whether they rise or fall in their daily performance of duty, they serve the will of the eternal Creator, bringing forth the beauty with which they are clothed and shining by day and by night. How often is the sun covered by clouds or taken from the gaze of the earth when the ray of its light is dispelled in the sky or an eclipse occurs, and as Scripture says: "The moon knows its going down." It knows when it should shine in full light or weakened light. The stars, which are engaged in service to this world's advantage, disappear when they are covered by clouds, not willingly, surely, but in hope, because they hope for gratitude for their labor from him who made them subject [to him]. Thus, they persevere for his sake, that is, for his will.”

“"He appointed the Moon for certain seasons" (ver. 19). We understand spiritually the Church increasing from the smallest size, and growing old as it were from the mortality of this life; yet so, that it draweth nearer unto the Sun. I speak not of this moon visible to the eye, but of that which is signified by this name. While the Church was in the dark, while she as yet appeared not, shone not forth as yet, men were led astray, and it was said, This is the Church, here is Christ; so that "while the Moon was dark, they shot their arrows at the righteous in heart." How blind is he who now, when the Moon is full, wandereth astray? "He appointed the Moon for certain seasons." For here the Church temporarily is passing away: for this subjection to death will not remain for ever: there will some time be an end of waxing and waning; it is appointed for certain seasons. "And the sun knoweth his going down." And what sun is this, but that Sun of righteousness, whom the ungodly will lament on the day of judgment never having risen for them; they who will say on that day, "Therefore we wandered from the way of truth, and the light of righteousness shone not on us, and the sun did not arise upon us." That sun riseth for him who understandeth Christ. ...”

“As you know, that psalm [104 (103 LXX)] contains the words "The sun knows the hour of its setting. You bring darkness, and it is night." What person, though unlettered, does not understand and know that when the sun reaches its setting, immediately night and darkness appear? Why, then, was it necessary for the prophet to say what is evidently understood by everyone? Likewise what follows: "Then all the beasts of the forest roam about. Young lions roar for the prey and seek their food from God." Can there be found anyone who does not know this? Truly, it is known to everyone that when night comes all the beasts roam about everywhere. Since, as you see, we ought not receive this according to the letter, listen attentively, as is your custom, to their spiritual significance.Now what the psalmist said, "The sun knows the hour of its setting," is not to be taken concerning the sun but with regard to him of whom the prophet says, "For those who fear your name there will arise the sun of justice with its healing rays." Of him we read in Solomon that the wicked will say, "The sun did not rise for us." Therefore, Christ is the true sun of justice. He knew his setting when he yielded to his passion for our salvation; for when he was crucified, night and darkness took hold of the souls of his disciples. Truly, brothers, how was there not darkness in those who did not believe Christ was risen from the dead? Finally, when the women reported that they had seen the Lord, "this talk seemed to the apostles to be nonsense, and they did not believe the women." Moreover, on another occasion the two disciples spoke thus to the Lord who was talking to them: "But we were hoping that it was he who should redeem Israel." When the apostles spoke these words, then was fulfilled those others: "The sun knows the hour of its setting. You bring darkness, and it is night."”