1 John 5:10-12

10The one who believes in the Son of God [who adheres to, trusts in, and relies confidently on Him as Savior] has the testimony within himself [because he can speak authoritatively about Christ from his own personal experience]. The one who does not believe God [in this way] has made Him [out to be] a liar, because he has not believed in the evidence that God has given regarding His Son.

11And the testimony is this: God has given us eternal life [we already possess it], and this life is in His Son [resulting in our spiritual completeness, and eternal companionship with Him].

12He who has the Son [by accepting Him as Lord and Savior] has the life [that is eternal]; he who does not have the Son of God [by personal faith] does not have the life.