James 5:20
20 Let him know, that he which converteth the sinner from the error of his way shall save a soul from death, and shall hide a multitude of sins.
The Grace New Testament Commentary - James 5:20
5:20 And these endeavors were well worthwhile. In fact, anyone who turns a sinner from the error of his way (hodou, "road") is in reality turning him aside from a sinful path that can lead him to his physical death (see James 1:15). Thus a Christian's efforts for the restoration of his brother to the pathway of obedience are life-saving in scope. If successful, he will save a soul (psychē, "life," "person") from death. But he will do more than that, since a restored sinner receives the gracious forgiveness of God. Thus the many sins created and multiplied by a man who turns away from God are all removed from view when that man turns back to God. The word rendered cover here (kalypsei) means "conceal." The restored sinner's multitude of sins are now out of sight through the pardon he has received. And the loving brother who turns him back is credited not only with the preservation of his fellow Christian's life, but also with making him clean, as if his efforts have removed from view all the unsightly moral disfigurements which sin creates, (though, of course, only the Lord actually cleanses anyone). Thanks to such personal involvement, the formerly erring Christian is both physically alive and spiritually clean.
And here the epistle ends. But in no sense is this ending flat or anticlimactic. On the contrary, in his impressive conclusion (James 5:7-20), James has carried his readers all the way from a state of grumbling against each other (v 9), to a loving mutual concern for one another's physical needs (see v 16), to the highest point of all: concern about a brother's sin (vv 19-20). When believers have reached this plateau, they have indeed surmounted their self-centered concern for their own trials and testings. They now have their eyes focused on the spiritual needs of their brothers and sisters, their hearts are lifted in prayer for them, and their hands are outstretched to draw them back onto the right road.