“A rebellious person seeks evil.” The text can also be translated, “An evil man seeks only rebellion.” Scholars argue for both positions. Keil and Delitzsch point out that the rebellious man seeking only after evil is a much more natural connection than the evil man seeking only rebellion.
“messenger.” The Hebrew is (#04397 מַלְאָך), and means, ”a messenger,” either human or divine. We call divine messengers, “angels,” and mal’ak occurs almost 200 times in the Old Testament, about half the time being translated “angel” (Gen. 19:1; 24:7), and the other half “messenger,” referring to a human messenger (Num. 21:21; Josh. 6:17). The Greek word aggelos (pronounced “an-ge-los”) also means “messenger” and is also translated both “angel” (Matt. 1:20; 13:41), and “messenger” (Luke 7:24; James 2:25). Angels are the messengers of God, who do his bidding in heaven and on earth. Although it may seem helpful to translate human messengers as “messengers” and divine messengers as “angels,” Proverbs 17:12 is a verse where that would cause problems. The rebellious person will have cruel “messengers,” sent against him, both human messengers and spirit messengers.
Rebellion in the heart of a man opens him up to demonic attack and affliction. We could translate the verse, “a cruel angel will be sent against him,” and that would be valid, but it would exclude human messengers. Sometimes it is human messengers who squash rebellion. For example, after David died, his son Adonijah began to set himself up to rebel against Solomon, but Solomon recognized the situation and sent Benaiah, a leader of his guard, to execute Adonijah (1 Kings 2:13-25). Rebellious people open themselves up to harsh and sometimes deadly attacks by both human and divine messengers: people, angels, or demons. [For more information on evil and ungodly behavior opening a person up to demonic attacks, see commentary on Prov. 13:21].