11. Having mentioned sins of the tongue (Jas 3:5-12), he shows here that evil-speaking flows from the same spirit of exalting self at the expense of one's neighbor as caused the "fightings" reprobated in this chapter (Jas 4:1).
      Speak not evil--literally, "Speak not against" one another.
      brethren--implying the inconsistency of such depreciatory speaking of one another in brethren.
      speaketh evil of the law--for the law in commanding, "Love thy neighbor as thyself" (Jas 2:8), virtually condemns evil-speaking and judging [ESTIUS]. Those who superciliously condemn the acts and words of others which do not please themselves, thus aiming at the reputation of sanctity, put their own moroseness in the place of the law, and claim to themselves a power of censuring above the law of God, condemning what the law permits [CALVIN]. Such a one acts as though the law could not perform its own office of judging, but he must fly upon the office [BENGEL]. This is the last mention of the law in the New Testament. ALFORD rightly takes the "law" to be the old moral law applied in its comprehensive spiritual fulness by Christ: "the law of liberty."
      if thou judge the law, thou art not a doer . . . but a judge--Setting aside the Christian brotherhood as all alike called to be doers of the law, in subjection to it, such a one arrogates the office of a judge.

JFB.