Psalms 19:5

Concerning the motion of the sun he says two things: "From the highest heaven." Note that he speaks of the heaven as it is in its motion, which is the end of the night and the beginning of the day. And insofar as it is …

Hence in the voice of this same Church it is said through Solomon, "Behold, he comes leaping upon the mountains and bounding over the hills." For she considered the heights of such great works and said, "Behold, he comes leaping upon the mountains." For in coming for our redemption, He made certain leaps, so to speak. Do you wish, dearest brothers, to recognize His very leaps? From heaven He came into the womb, from the womb He came into the manger, from the manger He came to the cross, from the cross He came into the tomb, from the tomb He returned to heaven. Behold, so that He might make us run after Him, the Truth made manifest through the flesh made certain leaps for us, because "He rejoiced as a giant to run His course," so that we might say to Him from the heart, "Draw us after You; we will run in the fragrance of Your ointments."

Bridegroom - Gloriously adorned with light as with a beautiful garment, and smiling upon the world with a pleasant countenance. Chamber - In which he is poetically supposed to have rested all night, and thence to break forth as it were on a sudden.

Which is as a bridegroom coming out of his chamber,....

"Which is as a bridegroom coming out of his chamber." A bridegroom comes forth sumptuously apparelled, his face beaming with a joy which he imparts to all around; such, but with a mighty emphasis, is the rising Sun. "And rejoiceth as a strong man to run a race." As a champion girt for running cheerfully addresses himself to the race, so does the sun speed onward with matchless regularity and unwearying swiftness in his appointed orbit. It is but mere play to him; there are no signs of effort, flagging, or exhaustion. No other creature yields such joy to the earth as her bridegroom the sun; and none, whether they be horse or eagle, can for an instant compare in swiftness with that heavenly champion. But all his glory is but the glory of God; even the sun shines in light borrowed from the Great Father of Lights. Thou sun, of this great world both eye and soul, Acknowledge Him thy greater; sound his praise Both when thou climb'st, and when high noon hast gained, And when thou fall'st."

Which is as a bridegroom, etc. - This is a reference to the rising of the sun, as the following verse is to the setting. He makes his appearance above the horizon with splendor and majesty; every creature seems to rejoice at his approach; and during the whole of his course, through his whole circuit, his apparent revolution from east to west, and from one tropic to the same again, no part of the earth is deprived of its proper proportion of light and heat. The sun is compared to a bridegroom in his ornaments, because of the glory and splendour of his rays; and to a giant or strong man running a race, because of the power of his light and heat. The apparent motion of the sun, in his diurnal and annual progress, are here both referred to. Yet both of these have been demonstrated to be mere appearances. The sun’s diurnal motion arises from the earth’s rotation on its axis from west to east in twenty-three hours, fifty-six minutes, and four seconds, the mean or equal time which elapses between the two consecutive meridian-transits of the same fixed star. But on account of the sun’s apparent ecliptic motion in the same direction, the earth must make about the three hundred and sixty-fifth part of a second revolution on its axis before any given point of the earth’s surface can be again brought into the same direction with the sun as before: so that the length of a natural day is twenty-four hours at a mean rate. The apparent revolution of the sun through the twelve constellations of the zodiac in a sidereal year, is caused by the earth’s making one complete revolution in its orbit in the same time. […]

Which is as a bridegroom coming out of his chamber - That is, when he rises in the morning. He rises from the darkness of the night, and comes forth as the bridegroom comes out of the chamber where he has slept. The allusion is to the bright, and joyful, and cheerful aspect of the rising sun. The image of the bridegroom is employed because we associate with a bridegroom the idea of hilarity, cheerfulness, joy.