Keil & Delitzsch, on Prov 15:26

26 An abomination to Jahve are evil thoughts; But gracious words are to Him pure. Not personally (Luther: the plans of the wicked) but neutrally is רע here meant as at Pro 2:14, and in אושׁת רע, Pro 6:24 (cf. Pers. merdi nı̂ku, man of good = good man), vid., Friedr. Philippi's Status Constr. p. 121. Thoughts which are of a bad kind and of a bad tendency, particularly (what the parallel member brings near) of a bad disposition and design against others, are an abomination to God; but, on the contrary, pure, viz., in His eyes, which cannot look upon iniquity (Hab 1:13), are the אמרי־נעם, words of compassion and of friendship toward men, which are (after 26a) the expression of such thoughts, thus sincere, benevolent words, the influence of which on the soul and body of him to whom they refer is described, Pro 16:24. The Syr., Targ., Symmachus, Theodotion, and the Venet. recognise in וּטהורים the pred., while, on the contrary, the lxx, Jerome, and Luther (who finally decided for the translation, "but the pure speak comfortably") regard it as subject. But that would be an attribution which exceeds the measure of possibility, and for which אמרים or דברי must be used; also the parallelism requires that טהורים correspond with 'תועבת ה. Hence also the reference of וטהורים to the judgment of God, which is determined after the motive of pure untainted law; that which proceeds from such, that and that only, is pure, pure in His sight, and thus also pure in itself.