Why is faith required, that we may receive benefit by Christ? For these reasons: 1. In respect of God; 2. In respect of Christ; 3. In respect of the creature; 4. In respect of our comforts.
1. In respect of God: that our hearts may be possessed with a full apprehension of His grace, Who in the New Covenant appeareth not as a revenging and condemning God, but as a pardoning God. This reason is rendered by the Apostle, “Therefore it is of faith, that it might be by grace” (Rom 4:16). The Law brought in the terror of God by being the instrument of revealing sin and the punishment due thereunto: “Because the law worketh wrath: for where no law is, there is no transgression” (4:15), no such stinging sense of it. But the gospel brought in grace. The Law stated the breach, but the gospel showed the way of our recovery. And therefore, faith doth more agree with grace, as it makes God more amiable and lovely to us, and beloved by us by the discovery of His goodness and grace. The saving of man by Christ, that is, by His incarnation, life, sufferings, death, resurrection, and ascension, all tends to possess our hearts with His abundant grace. To the same tend also His merciful covenant, gracious promises, and all the benefits given to us: His Spirit, pardon, and communion with God in glory, all is to fill our hearts with a sense of the love of God. And all this is no more than necessary. For a guilty conscience is not easily settled and brought to look for all kind of happiness from One Whom we have so much wronged. Adam, when once a sinner, was shy of God (Gen 3:30); and sin still makes us hang from Him. Guilt is suspicious, and if we have not one to lead us by the hand and bring us to God, we cannot abide His presence. For this end serveth faith: that sinners, being possessed of the goodness and grace of God, may be recovered and return to Him by a fit means. In the New Covenant, repentance more distinctly respects God, and faith respecteth Christ: “Repentance toward God, and faith toward our Lord Jesus Christ” (Act 20:21). Repentance respects God because from God we fell and to God we must return. We fell from Him, as we withdrew our allegiance and sought our happiness elsewhere; to Him we return, as our rightful and proper happiness.
But faith respects the Mediator, Who is the only remedy of our misery and the means of our eternal blessedness. He opened the way to God by His merit and satisfaction and actually bringeth us into this way by His renewing and reconciling grace, that we may be in a capacity to both please and enjoy God. And that is the reason why faith in Christ is so much insisted on as our title and claim to the blessedness of the New Covenant. It hath a special aptitude and fitness for our recovery from sin to God because it peculiarly respects the Mediator by Whom we come to Him.
2. In respect of Christ:
 Because the whole dispensation of grace by Christ cannot well be apprehended by anything but faith. Partly because the way of our recovery is so supernatural, strange, and wonderful, how can we be persuaded of it, unless we believe God’s testimony? That the carpenter’s son should be the Son of that Great Architect and Builder Who framed heaven and earth; that life should come to us by the death of another; that God should be made man, and the Judge a party; and He that knew no sin be condemned as a criminal person; that one crucified should procure the salvation of the whole world and be Lord of life and death and have such power over all flesh as to give eternal life to whom He will—reason is puzzled at these things. Faith only can unravel them...Sense only looks to things seen and felt; reason seeth effects in their causes...but faith is a believing such things as God hath revealed because He hath revealed them. Surely, this only can sustain us in the expectation of God’s grace and mercy unto eternal life. Whilst we are employed in duties so opposite to the bent of the carnal heart and have so many temptations to the contrary, what can support us but a strong and lively faith?
 Until we believe in Christ, we can have no comfort or use of all His offices. How can we learn of Him the way of salvation, until we believe Him to be the Prophet sent of God to teach the world the way to true happiness? “This is my beloved Son, in whom I am well pleased; hear ye him” (Mat 17:5). How can we obey Him, unless we believe in Him that He is our Lord, Who hath power over all flesh, at Whose judgment we must stand or fall? “[God] now commandeth all men every where to repent: Because he hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead” (Act 17:30-31). How can we depend upon the merit of His obedience and sacrifice, be comforted with His gracious promises and covenant, come to God with boldness and hope of mercy in His name, and be confident that He will justify, sanctify, and save us unless we believe that He is a Priest, Who once made an atonement and continually makes intercession for us? (Heb 9:25). In the days of His flesh, when any came for any benefit to Him, He put him upon this trial, “Believe ye that I am able to do this?” (Mat 9:28). “Jesus said unto him, If
thou canst believe, all things are possible to him that believeth” (Mar 9:23). “Believest thou this?” to Martha (Joh 11:26). Thus, they were not capable of any benefit until they believed.
3. With respect to that holiness and obedience that God expected from the creature: Christ came to restore us to God, which He doth as both a Savior and Lawgiver to His church. And until we believe in Him, both these qualities and functions miss of their effect.
 As a Savior, He came to take away the curse of the Law and to put us into a capacity to serve and please God by giving us His Spirit to renew our natures and heal our souls: “The chastisement of our peace was upon him; and with his stripes we are healed” (Isa 53:5). “Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed” (1Pe 2:24). We shall never mind our duty nor be capable to perform it, unless we believe that He is such a Savior.
 As a Lawgiver, obliging us by His authority to live in obedience unto God. The kingdom of the Mediator is clearly subordinate to the kingdom of God. For He came not to vacate our duty, but to establish it. He came to restore the lost groat to the owner, the lost sheep to the possessor, the lost son to the father. As the grace of Christ doth not vacate the mercy of God, so the authority of Christ...doth not free us from the authority of God. Now, who will submit to an authority that is not convinced of it or doth not believe it? But when once we believe, then we bow heart and knee.
4. With respect to our comfort: Often in Scripture, faith is represented as a quieting grace. The comfort, quietness, and peace of the soul dependeth much upon faith in Christ as an all-sufficient Savior, which banishes our fears and makes us in our greatest hardships to trust Christ with all our happiness, and to feast the soul with a constant peace and everlasting joy. Whether this world be turned upside down and be dissolved; whether we be in poverty and sickness, or in health or wealth; whether we be under evil repute or good; whether persecution or prosperity befall us, how little are we concerned in all these, if we know in Whom we have believed? (2Ti 1:12). Heaven is where it was before, and Christ is at the right hand of God. How little then should all these things disturb the peace and comfort of that soul that shall live with God forever? (Psa 112:7). But sin is our greatest trouble. If sin be your trouble, I answer, “Is it your infirmity or iniquity?” If infirmity, there is “no condemnation to them which are in Christ Jesus” (Rom 8:1). If iniquity, break off your sin by repentance; and then there may be comfort for you, for Christ came to save us from our sins.
USE 1: to confute men’s presumptions of their eternal good estate, whereby many damnably
delude their own souls.
1. Some, when they hear that whosoever believeth shall be saved, have a carnal notion of Christ. [They believe] that if He were alive, they would own Him, receive Him into their houses, and use Him more friendlily than the Jews did. This is but a knowing Christ “after the flesh” (2Co 5:16). He is not to be received into your houses, but into your hearts. Besides, we do not know our own hearts or what we should have done, if we had lived then. A person of such contemptible appearance as Christ was and so free in His reproofs of the sins of the times would not have been for our turn no more than theirs. The Jews said, “If we had been in the days of our fathers, we would not have been partakers with them in the blood of the prophets” (Mat 23:30). The memory of Korah, Dathan, and Abiram was as detestable to the carnal Jews as that of Judas and Pontius Pilate to Christians; but they were not a whit the better men, no more are we.
2. They do great reverence to His name and memory, profess themselves Christians, and abhor Turks and infidels. No, this will not do either. Many prize Christ’s name that neglect His office. Honoring the physician without taking his remedies never brought health. They have learned to speak well of Christ by rote after others, but they do not savingly and sincerely believe in Him to cure and heal their souls and suffer Him to do the work of a mediator there...
3. They are very willing to be forgiven by Christ and to obtain eternal life; but this is what mere necessity requires them. They will not suffer Him to do His whole work, to sanctify them, and fit them to live to God, nor part with their nearest and clearest lusts, and come into the obedience of the gospel; or at least, if Christ will do it for them, without their improving this grace or using His holy means, they are contented. But “having therefore these promises,” and such a blessed Redeemer, we are to “cleanse ourselves” (2Co 7:1). The work is ours, though the grace be from Him. So Galatians 5:24, “They that are Christ’s have crucified the flesh with the affections and lusts.”
4. Some have a strong conceit that they shall be saved and have benefit by Christ. This, which they call their faith, may be the greatest unbelief in the world; that men living in their sins shall yet do well enough is to believe the flat contrary of what God had spoken in His Word, “Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind...shall inherit the kingdom of God” (1Co 6:9-10). It is not strength of conceit, but the sure foundation of our hope, that will support us.
USE 2: Do we believe in the Son of God? Here will be the great case of conscience for settling our eternal interest.
1. If we believe, Christ will be precious to us: “Unto you therefore which believe he is precious” (1Pe 2:7). Christ cannot be accepted where He is not valued when other things come in competition with Him, and God will not be prodigal of His grace.
2. Where there is true faith, the heart will be purified: “Purifying their hearts by faith” (Act 15:9).
3. If you do believe in Christ, the heart will be weaned from the world: “For whatsoever is born of God overcometh the world; and this is the victory that overcometh the world, even our faith” (1Jo 5:4).
4. If you have the true faith, it works by love: “For in Jesus Christ neither circumcision availeth any thing, nor uncircumcision; but faith which worketh by love” (Gal 5:6).
By these things will the case be determined. Then the comfort and sweetness of this truth falls upon your hearts, that “God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life” (Joh 3:16).
From Sermon XVI, “Sermons upon John III.16” in The Complete Works of Thomas Manton, D.D., Vol. 2