Albert Barnes Commentary Job 37:13

"Whether it be for correction, or for his land, Or for lovingkindness, that he cause it to come." — Job 37:13 (ASV)

He causes it to come—That is, the rain, or the storm. It is entirely under the hand of God, like the lightning (Job 36:30), and designed to accomplish His purposes of mercy and of justice.

Whether for correction—The margin notes, as in Hebrew, “a rod.” The rod is often used as an emblem of punishment. The idea is, that God, when He pleases, can send the rain upon the earth for the purpose of executing punishment. So He did on the old world (Genesis 7:11–12), and so the overflowing flood is often now sent to sweep away the works of man, to lay waste his fields, and to cut off the wicked.

Or for His land—When necessary to render the land productive. He waters it by timely rains. It is called “His land,” meaning that the earth belongs to the Lord, and that He cultivates it as His own (Psalms 24:1).

Or for mercy—In kindness and benignity to the world. But for this, the earth would become baked and parched, and all vegetation would expire. The idea is, that the rains are entirely under the control of God, and that He can use them to accomplish His various purposes—to execute His judgments, or to express His benignity and love. These various uses to which the lightning, the storm, and the rain could be made subservient under the divine direction seem to have been one of the main ideas in the mind of Elihu, showing the supremacy and the majesty of God.