Charles Ellicott Commentary Psalms 144:4

"Man is like to vanity: His days are as a shadow that passeth away." — Psalms 144:4 (ASV)

Vanity ... shadow. —See Psalms 39:5-6; Psalms 102:11. The occasion of the introduction of these sentiments here is not quite clear. It may be the humility of the warrior who ascribes all success to God instead of to human prowess, or it may be a reflection uttered over the corpses of comrades, or, perhaps, a blending of the two.