1John 5:8-12 And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one. If we receive the witness of men, the witness of God is greater: for this is the witness of God which he has testified of his Son. He that believes on the Son of God hath the witness in himself: he that believes not God has made him a liar; because he believes not the record that God gave of his Son. And this is the record, that God has given to us eternal life, and this life is in his Son. He that has the Son has life; and he that has not the Son of God has not life. 

‘Three’ there are three witnesses of humanity and sonship: The Holy Spirit descending upon Jesus at His water baptism (Matt. 3:13-17). The water – a threefold witness: (1) Water baptism symbolizing His own death, burial, and resurrection (Matt. 3:13-17); (2) Water of the Word bearing witness to the incarnation (Isa. 7:14; 9:6-7; Matt. 1:23; Luke 1:34-35); (3) Water and blood at the crucifixion testifying of His humanity (John 19:34). The third witness is the blood, testifying not only the humanity and sonship of Jesus Christ but guaranteeing redemption from sin (Matt. 26:28; Acts 20:28; Eph. 1:14; Col. 1:20-22; Heb. 9:14-26; 10:1-23; 1Jn. 1:7).

‘Agree in one’ agree to the one point of the humanity and sonship of Jesus (4:1-6; 5:5-9).

‘If we receive the witness of men, the witness of God is greater; for this is the witness of God which he has testified of his Son’ if we receive witness of sinful men who can so easily deceive, we should gladly receive the witness of God who cannot possibly deceive. God’s witness of His Son is greater than all men.

‘He that believes on the Son of God has the witness in himself’ every believer has a personal witness from God to his faith (Rom. 8:14-16; Gal. 5:6; 2Cor. 5:17).

‘He that believes not God has made him a liar; because he believes not the record that God gave of his Son’ every unbeliever receives the fruit of his own rejection of God (John 3:36).

‘And this is the record, that God has given to us eternal life’ – eternal life in Jesus Christ is the great truth of which the Father, the Son, the Holy Spirit, the water, and the blood bear testimony.

‘This life is in his Son’ eternal life is only in Jesus. All who are in Him have this eternal life and all out of Him do not have it. Blessings in Jesus Christ: No condemnation (Rom. 8:1); freedom from the law of sin and death (Rom. 8:2); the love of God (Rom. 8:39); truth (Rom. 9:1); union in one body (Rom. 12:5); wisdom, righteousness, sanctification, and redemption (1Cor. 1:30; Rom. 3:24); resurrection of the body (1Cor. 15:22); triumph (2Cor. 2:14); abolishment of the Old Testament law; new creation (2Cor. 5:17); simplicity (2Cor. 11:3); liberty (Gal. 2:4); sonship (Gal. 3:26); brought close to God (Eph. 2:13); high calling (Php. 3:14); faith and love (1Tim. 1:14; 3:13); grace (2Tim. 2:1); salvation (2Tim. 2:10); eternal life (5:11; 2Tim. 1:1); preservation (Jude 1:1).