Charles Spurgeon Commentary James 4:11

"Speak not one against another, brethren. He that speaketh against a brother, or judgeth his brother, speaketh against the law, and judgeth the law: but if thou judgest the law, thou art not a doer of the law, but a judge." — James 4:11 (ASV)

If you cease to think what is evil, you will also cease to speak evil. If I speak evil of my brother, I have condemned the law which commands me to love him as I love myself; I have practically said that it is an absurd law, and an unrighteous law; and this is a great evil in God's sight.