God commands us to "earnestly contend for the faith once delivered to the saints", to beware of false teachers, false gospels, and doctrines of devils, and to separate ourself from heresy. (Matthew 7:15; Romans 16:17; 2 Corinthians 11:3; Ephesians 4:14; 1 Timothy 4:1-3; 2 Timothy 3:5; Titus 3:10-11; 2 Peter 2:1-2; Jude 3)