Theophylact of Ohrid, on Jas 4:14

“Whereas you know not what shall be on the morrow.”

“He shows the vanity of our life and puts us to shame for spending our entire life in vanity, for all our labor is exhausted on temporal evil. David says the same: "Surely every man walks about like a shadow; surely he busies himself in vain" ("Truly, man walks about like a phantom; in vain he bustles") (Ps. 39:6) — that is, he busies himself over what does not exist but appears as if in a shadow, or over what has no independent existence but constitutes merely a likeness and image of a truly flourishing life. Vapor is a dark compound arising from intense heat and moisture and having the briefest existence, for on account of its extreme fineness it quickly "vanishes" from contact with its surroundings, entering into them and dissolving, just as a small portion of moisture dissolves in water. This is what the apostle likened our "life" to, and most fittingly.”

Imported from an open dataset — not yet checked against the printed edition.