Albert Barnes Commentary Proverbs 1:11

"If they say, Come with us, Let us lay wait for blood; Let us lurk privily for the innocent without cause;" — Proverbs 1:11 (ASV)

The temptation against which the teacher seeks to guard his disciple is that of joining a band of highway robbers. The vain men who gathered around Jephthah (Judges 11:3), the lawless or discontented who came to David in Adullam (1 Samuel 22:2), the bands of robbers who infested every part of the country in the period of the New Testament, and against whom every Roman governor had to wage incessant war, show how deeply rooted the evil was in Palestine. Compare to Psalms 10:7 (see note) and Psalms 10:10 (see note).

Without cause - Better, in vain; most modern commentators join the words with innocent, and interpret them after (Job 1:9). The evil-doers deride their victims as being righteous in vain. They get nothing by it. It does them no good.