There are no data for ascertaining either the author or the date of this psalm. The variety of the figures employed seems to indicate a general view of life and its possible perils. It may have been a time when both war and pestilence were raging, but we cannot recover it. Whoever first breathed these words of trust, thousands have found them a source of strength and faith in the hour of trial and danger. Stier mentions that some years ago an eminent physician in St. Petersburg recommended this psalm as the best preservative against the cholera. It will also occur to every one that the psalm is the Hebrew, or, perhaps, rather the religious, expression of Horace’s ode,
“Integer vitæ seelerisque purus.”
The parallelism is fine and sustained.
 The omission of this word by a copyist would be very natural, from its confusion with the numerical heading of the psalm and the initial letter of the word that now begins it.
Psalm 91:2I will say of the LORD, He is my refuge and my fortress: my God; in him will I trust.
Psalm 91:3Surely he shall deliver thee from the snare of the fowler, and from the noisome pestilence.(3) Snare of the fowler.—The image of the net has occurred frequently before. (See Psalm 10:15, &c) Here, as in Ecclesiastes 9:12, it is used generally of any unexpected peril to life.
Noisome pestilence.—Literally, pestilence of calamities, i.e., fatal. (See Psalm 57:1, where the same word “calamities” occurs.)
“To bless the doors from nightly harm.”
In this case the arrow flying by day would refer to dangers of actual battle. But it is quite possible that the latter may be merely the Oriental expression for the pestilence, since it is still so called by Arabians. “I desired to remove to a less contagious air. I received from Solyman the emperor this message: that the emperor wondered what I meant in desiring to remove my habitation. Is not the pestilence God’s arrow, which will always hit his mark?”—Quoted in Spurgeon’s Treasury of David, from Busbequin’s Travels.
Destruction.—From a root meaning “to cut off;” here, from parallelism, “deadly sickness.”
“By every man, as he is born, there stands
A spirit good, a holy guide of life.”
Here, however, it is not one particular individual, but all who have fulfilled the conditions of Psalm 91:9-10 who are the objects of angelic charge. (Comp. Psalm 34:7.) (For the well-known quotation of this and Psalm 91:12 in the Temptation, see Matthew 4:6; Luke 4:10-11; with Notes in New Testament Commentary.)
(14) Set his love upon me.—Or, clung to me
Psalm 91:15He shall call upon me, and I will answer him: I will be with him in trouble; I will deliver him, and honour him.
Psalm 91:16With long life will I satisfy him, and shew him my salvation.(16) Long Life.—The promise of a long life, while in accordance with the general feeling of the Old Testament, is peculiarly appropriate at the close of this psalm, which all through speaks of protection from danger that threatened life.