John Gill Commentary James 2:9

"but if ye have respect of persons, ye commit sin, being convicted by the law as transgressors." — James 2:9 (ASV)

But if you have respect to persons, you commit sin ,
&c] This is not doing well, but is a transgression of the law, as every sin is; hence it follows,

and are convinced of the law as transgressors ;
which carries on a formal process against such persons; it accuses them of sin, and charges them with it; it proves it upon them, and convicts them of it; it pronounces them guilty, and curses them for it; and passes the sentence of condemnation and death upon them;

wherefore care should be taken not to commit this sin, and so fall under the convictions and reproofs of the law.