John Calvin Commentary Isaiah 50:3

"I clothe the heavens with blackness, and I make sackcloth their covering." — Isaiah 50:3 (ASV)

I clothe the heavens with blackness. He also mentions that thick darkness which was spread over all Egypt for three days (Exodus 10:22).

At that time, the heaven was clothed as with a mourning dress. For, as fine weather has a joyful influence, so blackness and darkness produce melancholy. Therefore, he says, that the heavens were covered as with sackcloth or with a mourning dress, as if they were tokens and expressions of mourning.

If anyone prefers to view them as general statements, let him enjoy his opinion. But I think it probable that he alludes to the history of the deliverance from Egypt, from 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.