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.
10 Whoever believes in the Son of God accepts this testimony. Whoever does not believe God has made him out to be a liar, because they have not believed the testimony God has given about his Son.
10 Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son.
10 Whoever believes in the Son of God inwardly confirms God's testimony. Whoever refuses to believe in effect calls God a liar, refusing to believe God's own testimony regarding his Son.
10 He who believes in the Son of God has the witness in himself; he who does not believe God has made Him a liar, because he has not believed the testimony that God has given of His Son.
10 All who believe in the Son of God know in their hearts that this testimony is true. Those who don't believe this are actually calling God a liar because they don't believe what God has testified about his Son.
Matthew Henry's Commentary on 1 John 5:10
Commentary on 1 John 5:9-12
(Read 1 John 5:9-12)
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 any one out of his senses who declined to do so. The real Christian has seen his guilt and misery, and his need of such a Saviour. He has seen the suitableness of such a Saviour to all his spiritual wants and circumstances. He has found and felt the power of the word and doctrine of Christ, humbling, healing, quickening, and comforting his soul. He has a new disposition, and new delights, and is not the man that he formerly was. Yet he finds still 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 a better. Such assurance has the gospel believer: he has a witness in himself, which puts the matter out of doubt with 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 that refuses to trust and honour 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 avail him.