New Defender's Study Bible Notes
11 way of Cain. Like Cain (Genesis 4:2-5; Hebrews 11:4), they reject the doctrine of redemption through the shed blood of a sinless substitute, the Lamb of God.
11 error of Balaam. Like Balaam (Numbers 22–24; II Peter 2:15-16), they use their religious connections not for the honor of God or the spread of His Word, but for their own personal agendas, whether money, pleasure, or power.
11 gainsaying of Core. Like Korah (Numbers 16:1-3,31-33), they reject God’s authority, as expressed in his day through Moses, and in our day through His inspired Word.