James 3:14

εἰ δὲ ζῆλον πικρὸν ἔχετε καὶ ἐριθείαν ἐν τῇ καρδίᾳ ὑμῶν : This makes it quite clear that what has been referred to all along is controversial strife; the bitter use of the tongue which the writer has been reprobating is the personal abuse which had been heaped upon one another by the partisans of rival schools of thought. ζῆλον is mostly used in a bad sense in the N.T., though the opposite is sometimes the case (e.g., 2 Corinthians 11:2; Galatians 1:14); the intensity of feeling which had been aroused among those to whom the Epistle was addressed is seen by the words ζῆλον πικρόν, with the latter word in an emphatic position; they form a striking contrast to πραΰτητι σοφίας. The word ἐριθείαν, derived from ἔριθος “a hireling,” means “party-spirit”. μὴ κατακαυχᾶσθε : the malicious triumphing at the least point of vantage gained by one party was just the thing calculated to embitter the other side; this was a real “lying against the truth,” because such petty triumphs are often gained at the expense of truth.