2:20 latter end is worse. It is thus very dangerous to know how to be saved and to understand the complete situation mentally, and then deliberately to turn Christ down. This is the same situation as described in Hebrews 6:4-6 and 10:26-31.
2:21 known the way of righteousness. Knowledge is necessary, but knowledge alone is insufficient for salvation. One must not only know the basic facts about salvation, but must receive Christ as personal Savior in true repentance and faith.
2:22 proverb. Proverbs 26:11 is cited here in part.