I walk about as a shadow. These are two very appropriate similitudes: to the first of them I formerly adverted in Psalm 102:12; namely, that the afflicted person, and he who is almost lifeless, is very fitly compared to the shadow of the evening. At sunrise, or when he is shining in noon-day brightness, the constant shifting of the shadow is not so perceptible; but, towards sunset, the shadow flits before us during every moment that passes. By the other similitude, the transitory nature of all sublunary things is pointed out. For as the locusts are constantly skipping from one place to another, so David complains of his life being ever rendered uneasy by incessant persecution, so that no space was allowed him for repose; and this is similar to what he says in Psalm 11:1, that he was compelled to flee like a sparrow, for which the fowler lays snares in all directions. In short, he mourns over his forlorn situation, that he could find no place of safety, and that, even among men, he could get no habitation. And, as in this psalm, he presents us with a picture of the whole Church, we need not be surprised if God try us, and arouse us from our lethargy, by an innumerable variety of events. Accordingly, Paul, 1-Corinthians 4:11, speaking of himself and others, says, that they have no certain dwelling-place; a description which is more or less applicable to all the children of God.

I am gone like the shadow when it declineth - See the notes at Psalm 102:11.
I am tossed up and down as the locust - Agitated, moved, driven about, as a cloud of locusts is by the wind. The meaning of the whole is, that he was frail and weak, and needed strength from on high.

I am gone like the shadow - "I have walked like the declining shadow," - I have passed my meridian of health and life; and as the sun is going below the horizon, so am I about to go under the earth.
I am tossed up and down as the locust - When swarms of locusts take wing, and infest the countries in the east, if the wind happen to blow briskly, the swarms are agitated and driven upon each other, so as to appear to be heaved to and fro, or tossed up and down. Dr. Shaw, who has seen this, says it gives a lively idea of the comparisons of the psalmist.

I am gone like the shadow when it declineth: I am tossed up and down as the (m) locust.
(m) Meaning that he has no stay or assurance in this world.

I am gone like the shadow when it declineth,.... When the sun is setting, and the shadow is going off; man's life is often compared to a shadow, because fleeting, momentary, and soon gone, 1-Chronicles 29:15 and death is expressed by going the way of all flesh; and by going to the grave, the house for all living, a man's long home, Joshua 23:14 and so is the death of Christ, Luke 22:22, it may be rendered, "I am made to go" (h), denoting the violent death of Christ, who was cut off out of the land of the living, and whose life was taken away from the earth, Isaiah 53:8.
I am tossed up and down as the locust; or "shaken out" (i) by the wind, as the locust is by the east wind, and carried from place to place, Exodus 10:13, or when a swarm of them by a strong wind are crowded together and thrown upon one another; or like the grasshopper, which leaps from hedge to hedge, and has no certain abode: and such was the case of Christ here on earth; and especially it may have respect not only to his being sometimes in Judea and sometimes in Galilee, sometimes in the temple and sometimes in the mount of Olives; but to his being tossed about after his apprehension, when he was led to Annas, and then to Caiaphas, then to Pilate, then to Herod, then delivered to the soldiers, and by them led to Calvary, and crucified.
(h) "cogor abire", Junius & Tremellius, Piscator, Cocceius; "abire factus sum", Gejerus, Michaelis. (i) "excussus sum", Montanus, Vatablus Gejerus, Michaelis; "excutior", Tigurine version, Musculus, Cocceius.

like the shadow--(Compare Psalm 102:11).
tossed up and down--or, "driven" (Exodus 10:19).

When - Towards the evening, when the sun is setting. The locust - Which is easily driven away with every wind.