James 1:4

4. ἔργον τέλειον, a perfect result, that result which is the τέλος of ὑπομονή, its final cause; opus consummatum O.L., o. perfectum 5. The character that repels and quenches evil results in perfectness and completeness. Each act of resistance strengthens character and developes new force, so completeness of resistance results in completeness of character.

τέλειοι are those who attain the aim or purpose for which they were intended and for which they were created, ὁλόκληροι (here and 1 Thessalonians 5:23 only in N.T.), those who retain all that was allotted to them from the first; comp. Acts 3:16 ἡ πίστις ἡ διʼ αὐτοῦ ἔδωκεν αὐτῷ τὴν ὁλοκληρίαν ταύτην, all this (physical) completeness. ὁλόκληρος is used (Ezekiel 15:5 LXX.) of a vine branch that is unimpaired: οὐδὲ ἔτι αὐτοῦ ὄντος ὁλοκλήρου οὐκ ἔσται εἰς ἐργσίαν, and very beautifully of perfect righteousness: τὸ γὰρ ἐπίστασθαί σε ὁλόκληρος δικαιοσύνη, Wis 15:3.

The germ of this thought is in our Lord’s words, Matthew 5:48 ἔσεσθε οὖν ὑμεῖς τέλειοι ὡς ὁ πατὴρ ὑμῶν ὁ οὐράνιος τέλειός ἐστιν. Comp. 2 Samuel 22:26 (Psalms 18:25). It is noticeable and suggestive that in the parallel passage, St Luke 6:36, οἰκτίρμονες and οἰκτίρμων take the place of τέλειοι and τέλειος. See also for τέλειοι Ephesians 4:13 μέχρι καταντήσωμεν … εἰς ἄνδρα τέλειον. Colossians 1:28 ἄνθρωπον τέλειον ἐν Χριστῷ.

ἐν μηδενὶ λειπόμενοι explains ὁλόκληροι.