Peter said "they have escaped the defilements of the world by the knowledge of the Lord and Savior Jesus Christ" (2Pe 2:20). "God has given us eternal life, and this life is in His Son" (1Jn 5:11). But Jesus said, "'If anyone does not abide in Me, he is thrown away as a branch and dries up'" (Jn 15:6). Branches "were broken off for their unbelief, but you stand by your faith" (Ro 11:20). You persevere by "keeping faith and a good conscience, which some have rejected and suffered shipwreck in regard to their faith" (1Ti 1:19). Therefore be careful "that there not be in any one of you an evil, unbelieving heart that falls away from the living God" (Heb 3:12). "The Spirit explicitly says that in later times some will fall away from the faith" (1Ti 4:1) and will "have fallen from grace" (Gal 5:4). Jesus said, "'There are some of you who do not believe'" (Jn 6:64) and "many of His disciples withdrew and were not walking with Him anymore" (:66).
If "they are again entangled in [defilements] and are overcome, the last state has become worse for them than the first" (2Pe 2:20). "It would be better for them not to have known the way of righteousness, than having known it, to turn away from the holy commandment handed on to them" (:21). But "we have become partakers of Christ, if we hold fast the beginning of our assurance" (Heb 3:14) and "our confidence and the boast of our hope firm until the end" (:6). Even Paul said "I discipline my body and make it my slave, so that, after I have preached to others, I myself will not be disqualified" (1Co 9:27). "Jesus said to the twelve, 'You do not want to go away also do you?' Simon Peter answered Him, 'Lord, to whom shall we go? You have words of eternal life. We have believed and have come to know that You are the Holy One of God'" (Jn 6:67-69).