God, Who cannot lie, promises eternal life!
1 John 2:24-25 (NLT) So you must remain faithful to what you have been taught from the beginning. If you do, you will remain in fellowship with the Son and with the Father. 25 And in this fellowship we enjoy the eternal life he promised us.
Titus 1:2 (NLT) This truth gives them confidence that they have eternal life, which God—who does not lie—promised them before the world began.
Who did He make this promise to? Eternal life is promised to all who believe in Jesus and believe that God raised Him from the dead. If you don’t believe that, then the promise of eternal life is not for you, however, it can be. Later in this writing, I’ll share how later.
John 3:36 (NLT) And anyone who believes in God’s Son has eternal life. Anyone who doesn’t obey the Son will never experience eternal life but remains under God’s angry judgment.”
How does He know who believes?
Romans 10:9 (NLT)9 If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved.
What is Eternal Life?
Eternal life is just not living forever; it is living forever in the Presence of God Almighty.
This from Dictionary.com and I think it’s a good one.
“eternal life in the Bible
This expression occurs in the Old Testament only in Dan. 12:2 (R.V., "everlasting life"). It occurs frequently in the New Testament (Matt. 7:14; 18:8, 9; Luke 10:28; comp. 18:18). It comprises the whole future of the redeemed (Luke 16:9), and is opposed to "eternal punishment" (Matt. 19:29; 25:46). It is the final reward and glory into which the children of God enter (1 Tim. 6:12, 19; Rom. 6:22; Gal. 6:8; 1 Tim. 1:16; Rom. 5:21); their Sabbath of rest (Heb. 4:9; comp. 12:22). The newness of life which the believer derives from Christ (Rom. 6:4) is the very essence of salvation, and hence the life of glory or the eternal life must also be theirs (Rom. 6:8; 2 Tim. 2:11, 12; Rom. 5:17, 21; 8:30; Eph. 2:5, 6). It is the "gift of God in Jesus Christ our Lord" (Rom. 6:23). The life the faithful have here on earth (John 3:36; 5:24; 6:47, 53-58) is inseparably connected with the eternal life beyond, the endless life of the future, the happy future of the saints in heaven (Matt. 19:16, 29; 25:46)”.- Easton's 1897 Bible Dictionary
Everlasting life, that is, life with no end in the awesome Presence of God, might be an even better way of explaining it.
One thing I can and need to tell you is that eternal life is forever; it can never be lost.
John 17:1-3 (NLT) 1 After saying all these things, Jesus looked up to heaven and said, “Father, the hour has come. Glorify your Son so he can give glory back to you. 2 For you have given him authority over everyone. He gives eternal life to each one you have given him. 3 And this is the way to have eternal life—to know you, the only true God, and Jesus Christ, the one you sent to earth.
Eternal Life is a Gift
God promises eternal life. There’s nothing you can do to earn it. God gives it as a gift by His grace. You can have His gift by not trusting in your own righteousness but by trusting in the righteousness of the one person who never sinned, Jesus Christ, God’s perfect substitute for our sin.
Romans 3:23-26 (NLT) 23 For everyone has sinned; we all fall short of God’s glorious standard. 24 Yet God, with undeserved kindness, declares that we are righteous. He did this through Christ Jesus when he freed us from the penalty for our sins. 25 For God presented Jesus as the sacrifice for sin. People are made right with God when they believe that Jesus sacrificed his life, shedding his blood…
2 Corinthians 5:21 (NLT) For God made Christ, who never sinned, to be the offering for our sin, so that we could be made right with God through Christ.