Albert Barnes Commentary Psalms 91:6

"For the pestilence that walketh in darkness, Nor for the destruction that wasteth at noonday." — Psalms 91:6 (ASV)

Nor for the pestilence - The plague or pestilence was common in Eastern countries.

That walketh in darkness - Not that it particularly comes in the night, but that it seems to creep along as if in the night; that is, where one cannot track its progress, or anticipate when or whom it will strike. The laws of its movements are unknown, and it comes upon people as an enemy that suddenly attacks us in the night.

Nor for the destruction - The word used here—קטב qeṭeb—properly means a cutting off, a destruction, as a destroying storm (Isaiah 28:2); and then, contagious pestilence (Deuteronomy 32:24). It may be applied here to anything that sweeps away people—whether storm, war, pestilence, or famine.

That wasteth at noonday - It lays waste, or produces desolation, at noon; that is, visibly, openly. The meaning is that whenever, or in whatever form, calamity comes that sweeps away people—whether at midnight or at noon, whether in the form of pestilence, war, or famine—he who trusts in God need not—and will not—be afraid.

He will feel either that he will be preserved from its ravages, or that if he is cut off, he has nothing to fear. He is a friend of God and has a hope of a better life. In death and in the future world, there is nothing of which he should be afraid.

The Septuagint and the Latin Vulgate render this, strangely enough, “Nor of mischance and the demon of noonday.”