A.T. Robertson Commentary James 5:12

"But above all things, my brethren, swear not, neither by the heaven, nor by the earth, nor by any other oath: but let your yea be yea, and your nay, nay; that ye fall not under judgment." — James 5:12 (ASV)

Above all things (προ παντων). No connection with what immediately precedes. Probably an allusion to the words of Jesus (Matthew 5:34–37). It is not out of place here. See the same phrase in 1 Peter 4:8. Robinson (Ephesians, p. 279) cites like examples from the papyri at the close of letters. Here it means "But especially" (Ropes).

Swear not (μη ομνυετε). Prohibition of the habit (or to quit doing it if guilty) with μη and the present active imperative of ομνυω. The various oaths (profanity) forbidden (μητε, thrice) are in the accusative case after ομνυετε, according to rule (ουρανον, γην, ορκον). The Jews were wont to split hairs in their use of profanity, and by avoiding God's name imagine that they were not really guilty of this sin, just as professing Christians today use "pious oaths" which violate the prohibition of Jesus.

Let be (ητω). Imperative active third singular of ειμ, late form (1 Corinthians 16:22) for εστω. "Your yea be yea" (and no more). A different form from that in Mt 5:37.

That ye fall not under judgment (ινα μη υπο κρισιν πεσητε). Negative purpose with ινα μη and the second aorist active subjunctive of πιπτω, to fall. See ινα μη κριθητε in verse 9. Κρισις (from κρινω) is the act of judging rather than the judgment rendered (κριμαJames 3:1).