Hast thou commanded the morning since thy days; and caused the dayspring to know his place; Hast thou commanded the morning - This refers to dawn or morning twilight, occasioned by the refraction of the solar rays by means of the atmosphere; so that we receive the light by degrees, which would otherwise burst at once upon our eyes, and injure, if not destroy, our sight; and by which even the body of the sun himself becomes evident several minutes before he rises above the horizon.
Caused the dayspring to know his place - This seems to refer to the different points in which daybreak appears during the course of the earth's revolution in its orbit; and which variety of points of appearing depends on this annual revolution. For, as the earth goes round the sun every year in the ecliptic, one half of which is on the north side of the equinoctial, and the other half on its south side, the sun appears to change his place every day. These are matters which the wisdom of God alone could plan, and which his power alone could execute. It may be just necessary to observe that the dawn does not appear, nor the sun rise exactly in the same point of the horizon, two successive days in the whole year, as he declines forty-three degrees north, and forty-three degrees south, of east; beginning on the 21st of March, and ending on the 22d of December; which variations not only produce the places of rising and setting, but also the length of day and night. And by this declination north and south, or approach to and recession from the tropics of Cancer and Capricorn, the solar light takes hold of the ends of the earth, Job 38:13, enlightens the arctic and antarctic circles in such a way as it would not do were it always on the equinoctial line; these tropics taking the sun twenty-three and a half degrees north, and as many south, of this line.