Charles H. Spurgeon wrote, "As a believer, you are one with Jesus. Therefore you are secure. You will be confirmed to the end until the day of his appearing." In these words, Spurgeon spoke of every believer's security in Jesus Christ.
Our security in Christ is through the gospel. We are one with Jesus through his death and resurrection (Romans 6:5-6). We have died to the old life. We are buried with Christ. We are risen with him unto newness of life. Water baptism is the symbol of our death, burial and resurrection with Christ (Romans 6:3-4). Therefore, Charles H. Spurgeon said, "As a believer, you are one with Jesus."
Our security in Christ is through new birth. Every true believer is born of the Spirit. We have been born again unto faith in our Lord Jesus Christ. As we are in Adam through our first birth, so we are in Christ through new birth. "Therefore, if anyone is in Christ, he is a new creation"(2 Corinthians 5:17).
Our security is in the body of Christ, through the Holy Spirit. We are baptized with the Holy Spirit into the body of Christ (1 Corinthians 12:13). Christ is the head, and we are the body. As Adam was the head of the human race, so Christ is the head of the church, which is his body (Colossians 1:18).
Our security is through the righteousness of Christ. As the human race is in Adam through sin and death, so believers are in Christ through salvation from sin and death (Romans 5:19; 1 Corinthians 15:22). We are born with a sinful nature in Adam, so we are born again unto righteousness in Christ as believers (2 Corinthians 5:21). Christ is our righteousness.