1 John 5:
9 If we receive the witness of men, the witness of God is greater: for this is the witness of God which he hath testified of his Son.
10 He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.
11 And this is the record, that God hath given to us eternal life, and this life is in his Son.
12 He that hath the Son hath life; and he that hath not the Son of God hath not life.
13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
14 And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us:
15 And if we know that he hear us, whatsoever we ask, we know that we have the petitions that we desired of him.
16 If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
17 All unrighteousness is sin: and there is a sin not unto death.
16 We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not.
19 And we know that we are of God, and the whole world lieth in wickedness.
20 And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
21 Little children, keep yourselves from idols. Amen.
Eternal life is in God's Son (vs 11).
He who has the Son has life and he who does not have the son does not have life (vs 12).
Believe on the name of the Son of God and you know you have eternal life (vs 13).
The Son of God gives us an understanding that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life (vs 20).
Eternal life is eternal life.