I clothe the heavens with blackness. He mentions also that thick darkness which was spread over all Egypt during the space of three days. (Exodus 10:22.) At that time the heaven was clothed as with a mouming dress; for, as fine weather has a gladdening influence, so blackness and darkness produce melancholy; and therefore he says, that the heavens were covered as with sackcloth or with a mouming dress, as if they had been tokens and expressions of mouming, [1] If any one prefer to view them as general statements, let him enjoy his opinion; but I think it probable that he glances at the history of the deliverance from Egypt, [2] front which it might easily be inferred that God, who had so miraculously assisted the fathers, was prevented by their ingratitude from granting relief to the miseries which now oppressed them.

Footnotes

1 - "This gives a great idea of God's power. Though the sun shines so bright that no mortal eye can steadily behold its lustre, I can at pleasure send a thick cloud and intercept its rays, and make the heavens appear as if they had put on mourning." -- White.

2 - "A l'histoire de la deliverance d'Egypte."

I clothe the heavens with blackness - With the dark clouds of a tempest - perhaps with an allusion to the remarkable clouds and tempests that encircled the brow of Sinai when he gave the law. Or possibly alluding to the thick darkness which he brought over the land of Egypt (Exodus 10:21; Grotius). In the previous verse, he had stated what he did on the earth, and referred to the exhibitions of his great power there. He here refers to the exhibition of his power in the sky; and the argument is, that he who had thus the power to spread darkness over the face of the sky, had power also to deliver his people.
I make sackcloth their covering - Alluding to the clouds. Sackcloth was a coarse and dark cloth which was usually worn as an emblem of mourning (see the note at Isaiah 3:24). The same image is used in Revelation 6:12 : 'And I beheld when he had opened the sixth seal, and lo, there was a great earthquake; and the sun became black as sackcloth of hair.' To say, therefore, that the heavens were clothed with sackcloth, is one of the most striking and impressive figures which can be conceived.

I clothe the heavens with blackness, and I make (f) sackcloth their covering.
(f) As I did in Egypt in token of my displeasure, (Exodus 10:21).

I clothe the heavens with blackness,.... With gross and thick darkness; perhaps referring to the three days' darkness the Egyptians were in, Exodus 10:12, or with thick and black clouds, as in tempestuous weather frequently; or by eclipses of the sun; there was an extraordinary instance of great darkness at the time of Christ's crucifixion, Matthew 27:45.
and I make sackcloth their covering; that being black, and used in times of mourning; the allusion may be to the tents of Kedar, which were covered with sackcloth, or such like black stuff. The fall of the Pagan empire, through the power of Christ and his Gospel, is signified by the sun becoming black as sackcloth of hair, Revelation 6:12. Jarchi interprets this parabolically of the princes of the nations, when the Lord shall come to take vengeance upon them; as Kimchi does the sea, and the rivers, in the preceding verse, of the good things of the nations of the world, which they had in great abundance, and should be destroyed.

heavens . . . blackness--another of the judgments on Egypt to be repeated hereafter on the last enemy of God's people (Exodus 10:21).
sackcloth-- (Revelation 6:12).

I clothe - When it is necessary to save my people, I cover them with thick and dark clouds black as sackcloth, Revelation 6:12.