James
James 4:17ESV·traditional attribution

So whoever knows the right thing to do and fails to do it, for him it is sin.

Matthew Henry Presbyterian @wholebiblehenry

In this part of the chapter, I. We are cautioned against the sin of evil-speaking: Speak not evil one of another, brethren, Jam 4:11. The Greek word, katalaleite, signifies speaking any thing that may hurt or injure another; we must not speak evil things of others, though they be true, unless we be called to it, and there be some necessary occasion for the; much...

Commenting on James 4:11-17

John Gill Reformed Baptist @doctorgill

Therefore to him that knoweth to do good,.... This may regard not only the last particular of referring all things to the will of God, the sovereign disposer of life, and all events, which some might have the knowledge of in theory, though they did not practise according to it; but all the good things the apostle had exhorted to, and the contrary to which...

Albert Barnes Presbyterian @notesbybarnes

Verse 17. Therefore to him that knoweth to do good, and doeth it not, to him it is sin. That is, he is guilty of sin if he does not do it. Cottoa Mather adopted it as a principle of action, "that the ability to do good in any case imposes an obligation to do it." The proposition in the verse before us is of...