1 John 5:12

He who has the Son has life; he who does not have the Son of God does not have life.

(v12, NIV)

The testimony of God is concerning his son. Specifically, the last verse focuses in on eternal life. This eternal life is through God's son, so the testimony is still referring to Jesus. This life or eternal life is in the Son. Therefore, if you want this life, you must have the Son. So in this verse, it is clearly stated that those who have the son have life, and those who do not have the son do not have life. What's interesting is that it doesn't say "eternal life", but it only says "life". God gives us eternal life and this life is in his son. Not only do these people who do not have the son not have eternal life, but they don't have life at all. This life is in his son, and to have Jesus is to have life. To not have Jesus is to not have life at all. It is only through Jesus that we may live.