Answer: Jesus says that eternal life is when a person KNOWS the only true God, and KNOWS Jesus Christ, Who was sent by God, (verse 3).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
John 4:14: [Jesus said,] "but whoever drinks the water I give him will never thirst. Indeed, the water I give him will become in him a spring of water welling up to eternal life."
John 5:24-25: [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. I tell you the Truth, a time is coming and has now come when the dead will hear the voice of the Son of God and those who hear will live."
John 6:27: [Jesus said,] "Do not work for food that spoils, but for food that endures to eternal life, which the Son of Man will give you. On Him God the Father has placed His seal of approval."
John 6:68-69: "Simon Peter answered Him, ‘Lord, to whom shall we go? You have the Words of eternal life. We believe and know that You are the Holy One of God.'"
John 12:25-26: [Jesus said,] "The man who loves his life will lose it, while the man who hates his life in this world will keep it for eternal life. Whoever serves Me must follow Me; and where I am, My servant also will be. My Father will honor the one who serves Me."
John 12:49-50: [Jesus said,] "For I did not speak of My Own accord, but the Father Who sent Me commanded Me what to say and how to say it. I know that His command leads to eternal life. So whatever I say is just what the Father has told Me to say."
John 14:6-10: "Jesus answered, ‘I am the Way and the Truth and the Life. No one comes to the Father except through Me. If you really knew Me, you would know My Father as well. From now on, you do know Him and have seen Him.' Philip said, ‘Lord, show us the Father and that will be enough for us.' Jesus answered: ‘Don't you know Me, Philip, even after I have been among you such a long time? Anyone who has seen Me has seen the Father. How can you say, "Show us the Father"? Don't you believe that I am in the Father, and that the Father is in Me? The Words I say to you are not just My Own. Rather, it is the Father, living in Me, Who is doing His work.'"
