I. What believing on the Son of God means.—II. What this inward witness is, that faith gives to christianity.—III. What sort of witness it is, and how it exceeds other testimonies in several respects. And, _Lastly_, We shall make some inferences. I. What is meant in my text by _believing on the Son of God_? I answer briefly under these two heads. It is,—1. A believing Jesus Christ to be the Saviour of the world.—2. A trust in Christ Jesus as our Saviour. 1. It is a _believing_ Jesus Christ _to be the Saviour of the world_; and in this manner it is often expressed by our apostle in these epistles: a belief that Jesus Christ is the Messiah, who was foretold by all the prophets, and represented by all the types and shadows of the Old Testament. This usually includes a belief of the most important things that are related in the gospel concerning his person; such as these, that he is true God and true man, _i. e._ that God and man are united in him; that he was the Son of God before all ages, and the son of man born in time. _That he was the seed of David after the flesh, but declared to be the Son of God with power by the resurrection from the dead_; Rom. i. 3, 4. That he is that eternal Word, who _in the beginning was with God, and was God_, and who was in due time _made flesh and tabernacled among us_, as in John i. 14. This is that _mystery of godliness_ which we must believe, _God manifest in the flesh_; 1 Tim. iii. 16. It implies also our belief of his doctrine, as well as of the divinity and humanity united in his person; _viz._ That we are all sinners condemned by the law of God; enemies to God in our minds, transgressors in our lives, and exposed to eternal death: That the divine law is so strict, so perfect, so holy, and so just that no mere man since the fall can fulfil it, nor yet can excuse or free himself from the condemnation of it: That Christ himself came _to fulfil this law_, as he tells us in Mat. v. 17, 18. That he came not only to perform the duties of it by an active obedience, but to put himself under the curse and condemnation for our sakes. Which the apostle to the Galatians expresses in this language, that _in the fulness of time he was made under the law_ to become _a curse for us_, that we who are under the law _might be redeemed from the curse, and receive a blessing_; Gal. iii. 13. and iv. 5. That _he died for our offences_, that _he rose again for our justification_; and that he has received the spirit of holiness, which he sends into our sinful natures, to form us fit for that heavenly inheritance which he hath purchased for us by his death. That without this purification of our natures, we can have no hope of heaven, for _without_ repentance and _holiness no man shall see God_. That Jesus Christ our Lord shall raise the dead, shall come in the last day to judge the world, and pass a decisive sentence, and shall then _reward every one according to their works_. Though all these things were not so