Neither have I suffered my mouth to sin by wishing a curse to his soul.
Mouth - literally, palate (Job 6:30, note).
Wishing - literally, 'so as to demand his (my enemy's) soul (i:e., life) by a curse.' This verse parenthetically confirms Job 31:29. Job, in the patriarchal age of the promise, anterior to the law, realizes the Gospel spirit, which was the end of the law (cf. Leviticus 19:18; contrast Deuteronomy 23:6 with Matthew 5:43-44).