Matthew Henry Commentary 1 John 5:9-12

"If we receive the witness of men, the witness of God is greater: for the witness of God is this, that he hath borne witness concerning his Son. He that believeth on the Son of God hath the witness in him: he that believeth not God hath made him a liar; because he hath not believed in the witness that God hath borne concerning his Son. And the witness is this, that God gave unto us eternal life, and this life is in his Son. He that hath the Son hath the life; he that hath not the Son of God hath not the life." — 1 John 5:9-12 (ASV)

Nothing can be more absurd than the conduct of those who doubt as to the truth of Christianity, while in the common affairs of life they do not hesitate to proceed on human testimony, and would deem anyone out of his senses who declined to do so. The real Christian has seen his guilt and misery, and his need of such a Savior. He has seen the suitability of such a Savior to all his spiritual wants and circumstances.

He has found and felt the power of the word and doctrine of Christ, humbling, healing, life-giving, and comforting his soul. He has a new disposition, and new delights, and is not the man that he formerly was. Yet he still finds a conflict with himself, with sin, with the flesh, the world, and wicked powers. But he finds such strength from faith in Christ, that he can overcome the world, and travel on towards what is better.

Such assurance has the gospel believer: he has a witness in himself, which puts the matter beyond doubt for him, except in hours of darkness or conflict; but he cannot be argued out of his belief in the leading truths of the gospel. Here is what makes the unbeliever's sin so awful; the sin of unbelief. He gives God the lie; because he believes not the record that God gave of his Son.

It is in vain for a man to plead that he believes the testimony of God in other things, while he rejects it in this. He who refuses to trust and honor Christ as the Son of God, who disdains to submit to his teaching as Prophet, to rely on his atonement and intercession as High Priest, or to obey him as King, is dead in sin, under condemnation; nor will any outward morality, learning, forms, notions, or confidences be of any avail to him.