Let him know, that he which converteth the sinner from the error of his way
Let him (the converter) know - for his encouragement.
Shall save - future. The salvation of the converted shall be manifested hereafter.
Shall hide a multitude or sins - not his own, but of the converted х kalupsei (G2572) (active voice) requires this]; Proverbs 10:12 (cf. note) refers to charity 'covering' the sins of others before men; James to one's effecting by another's conversion that that other's sins be covered before God-namely (Psalms 32:1), by making the convert partaker in Christ's atonement for the remission of all sins. Though this hiding of sins was included in "shall save," James expresses it to mark the greatness of the blessing conferred on the penitent through the converter's instrumentality, and so incite others to the same good deed.