A.T. Robertson Commentary James 4:14

"whereas ye know not what shall be on the morrow. What is your life? For ye are a vapor, that appeareth for a little time, and then vanisheth away." — James 4:14 (ASV)

Whereas ye know not (οιτινες ουκ επιστασθε). The longer relative οστις defines here more precisely (like Latin qui) ο λεγοντες (ye who say) of verse 13 in a causal sense, as in Ac 10:47, "who indeed do not know" (present middle indicative of επισταμα).

What shall be on the morrow (της αυριον). Supply ημερας (day) after αυριον. This is the reading of B (Westcott) "on the morrow" (genitive of time), but Aleph K L cursives have το της αυριον ("the matter of tomorrow"), while A P cursives have τα της αυριον ("the things of tomorrow"). The sense is practically the same, though το της αυριον is likely correct.

What is your life? (ποια η ζωη υμων). Thus Westcott and Hort punctuate it as an indirect question, not direct. Ποια is a qualitative interrogative (of what character).

As vapour (ατμις). This is the answer. Old word for mist (like ατμος, from which our "atmosphere"), in N.T. only here and Ac 2:19 with καπνου (vapour of smoke (from Joe 2:30).

For a little time (προς ολιγον). See same phrase in 1 Timothy 4:8, προς καιρον in Lu 8:13, προς ωραν in Joh 5:35.

That appeareth and then vanisheth away (φαινομενη επειτα κα αφανιζομενη). Present middle participles agreeing with ατμις, "appearing, then also disappearing," with play on the two verbs (φαινομαι, αφανιζω as in Mt 6:19, from αφανης hidden Heb 4:13) with the same root φαν (φαινω, α-φαν-ης).