God promises eternal life to those who believe in His Son. It's in the Bible, John 3:16, NIV. "For God so loved the world that He gave His one and only Son, that whoever believes in Him shall not perish but have eternal life."

Eternal life is a gift given to those who trust in Jesus. It's in the Bible, I John 5:11-12, NIV. "And this is the testimony: God has given us eternal life, and this life is in His Son. He who has the Son has life; he who does not have the Son of God does not have life."