Elsewhere in the New Testament, doubt signifies those who are in inner conflict (Acts 10:20; Romans 14:23; James 1:6). Jude is encouraging the church to rescue those who have erred or are attracted by the doctrine of the teachers whom he opposes. He’s not necessarily referring to three different groups but rather three ways of describing people in need of rescue.1 Mercy would then mean that the church must have a gracious attitude to these people, not condemning them for their uncertainty but seeking to win them back to Christ.2
22 And have mercy on those who doubt;