Biblical explanation
Some passages emphasize security. Jesus said His sheep hear His voice, follow Him, and receive eternal life (John 10:27-29). Other passages emphasize the necessity of continuing in faith. Colossians 1:21-23 speaks of being presented holy "if ye continue in the faith grounded and settled." Hebrews 3:14 says, "we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end." Jesus' teaching in John 15 is particularly important. He describes believers as branches connected to the vine and tells them to "abide" in Him (John 15:1-6). A branch that does not remain connected eventually withers. Paul also warned believers not to become proud but to "continue in his goodness" (Romans 11:20-22). These warnings do not undermine God's grace. They emphasize the reality of human choice and the necessity of continuing relationship with Christ. The Christian's confidence is therefore not confidence in oneself. It is confidence in Christ while continuing to abide in Him.
Key takeaway
Salvation is entirely by grace through faith in Christ. His atoning sacrifice, heavenly ministry, and intercession are the foundation of assurance; obedience, Sabbath faithfulness, and loving service are the fruit of a redeemed life, never a way to purchase acceptance with God.