The apostle John, under the inspiration of the Holy Spirit, revealed the glorious promise of the Gospel with these words, "I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life" (1 John 5:13). This verse parallels John's purpose for writing his Gospel: "these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name" (John 20:31). John wrote his Gospel so that people would believe and be saved. He wrote his first epistle so that those who believe would know they are saved.

Ignoring these certain and sure promises of God, over half of professing Christians believe they can lose their salvation. They believe eternal life is really conditional life and it is based on what they continue to do instead of what Christ has done. They say they believe in Jesus, but they do not believe what he promises. Jesus said, "I tell you the truth, whoever hears my word and believes Him who sent me has eternal life and will not be condemned, he has crossed over from death to life" (John 5:24). Those who are depending on their own righteousness, performing good works, or adhering to a religious system, can never be assured of salvation. They will never know if they have ever done enough. There is no joy when people put their faith in what they do instead of what God has done in Christ. When salvation depends completely on God, there is no chance for failure. Whenever man is involved in attaining and preserving salvation there can be no assurance, only a false hope. 

True believers have assurance through God the Father. Jesus said: "I give them eternal life, and they shall never perish...My Father, who has given them to Me, is greater than all; no one can snatch them out of my Father's hand" (John 10:28-29). The life Jesus gives is everlasting, not temporal or perishable. 

True believers also have assurance through God the Son. Jesus said: "This is the will of the Father who sent Me, that of all He has given Me I should lose nothing, but should raise it up at the last day. And this is the will of Him who sent Me, that everyone who sees the Son and believes in Him may have everlasting life; and I will raise him up at the last day" (John 6:39-40). "Everlasting" and "eternal" are words that describe not only the life believers have in Christ, but also the punishment that awaits those who die without Christ. 

Born-again Christians also have assurance through God the Holy Spirit. The Apostle Paul declared: "You also were included in Christ when you heard the word of truth, the Gospel of your salvation; having believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance" (Ephesians 1:13-14). At the very moment anyone understands and believes the Gospel, they are sealed by the Holy Spirit, who guarantees they will be co-heirs with Christ (Romans 8:17).

Assurance is based on God's power and promises (1 Pet. 1:3-5). The gift of eternal life is eternally secure because God's gifts are "irrevocable" (Romans 11:29). Eternal life can only be received as a gift of God's grace. Anyone who tries to earn or merit the gift nullifies God's grace (Rom. 11:6). Professing Christians who want to be certain of their salvation must believe the promises of the Gospel and repent of any teaching, experience or feeling that opposes the Word of God. Once they do, they will be more certain of living eternally in heaven than one more day on earth.