…He that believeth not God hath made Him a liar, because he believeth not the record that God gave of his Son.
1 JOHN 5:10
True faith must always rest upon what God is, so it is of utmost importance that, to the limit of our comprehension, we know what He is.
The psalmist said: “They that know thy name will put their trust in Thee,” the name of God being the verbal expression of His character, and confidence always rises or falls with known character.
What the psalmist said was simply that they who know God to be the kind of God He is will put their confidence in Him! This is not a special virtue, but the normal direction any mind takes when confronted with the fact. We are so made that we trust good character and distrust its opposite, and that is why unbelief is so intensely wicked!
The character of God, then, is the Christian’s final ground of assurance and the solution of many, if not most, of his practical religious problems.
Though God dwells in the center of eternal mystery, there need be no uncertainty about how He will act in any situation covered by His promises. These promises are infallible predictions. God will always do what He has promised to do when His conditions are met. And His warnings are no less predictive: “The ungodly shall not stand in the judgment, nor sinners in the congregation of the righteous” (Ps. 1:5).
We cultivate our knowledge of God and at the same time cultivate our faith. Yet while so doing we look not at our faith but at Christ, its author and finisher!
5:10 When a man does accept His testimony concerning His Son, God seals the truth by giving the man the witness of the Spirit in himself. On the other hand, if a man disbelieves God, he makes Him a liar; because he has not believed the testimony that God has given of His Son. People think they can accept or reject God’s testimony concerning Christ, but John would have them know that to reject it is to accuse God of dishonesty.
10. Anyone who believes in the Son of God has this testimony in his heart. Anyone who does not believe God has made him out to be a liar, because he has not believed the testimony God has given about his Son.
Throughout the epistle John uses contrast and this text is no exception. First he states the positive and then the negative.
In verse 10, belief in the Son of God is central; it is part of the message John teaches in verses 1–12, namely, faith in Jesus as the Son of God. Believing, says John, is a continuous act. That is, faith is a lasting and active power that resides in the heart of the believer. Faith is the constant bond between the Son of God and the believer.
Note that John states specifically that faith is believing in the Son of God. The preposition in means that the believer puts full trust and confidence in Jesus Christ, the Son of God. The believer has accepted the testimony (see John 3:33; Rom. 8:16) which God, through the Spirit, has given about his Son. And this testimony which comes to him through external witnesses is now lodged in his heart and has become an integral part of his spiritual life.
The second part of verse 10 is not a parallel of the first part. Instead of writing, “Anyone who does not believe in the Son of God,” John says, “Anyone who does not believe God.” He places the emphasis on God, who has given man testimony about his Son. Man, however, cannot accept this testimony merely for information. He does not have the freedom to take or leave it without obligation, for God gives him this testimony with royal authority. When man rejects God’s testimony, he has made and continues to make God a liar (compare 1:10). And this is a serious offense, because rejection of God’s Word constitutes deliberate unbelief.
John addressed the false teachers of his day, who said that they believed in God but rejected the birth and the death of his Son. John, however, addresses his word to anyone who rejects God’s testimony. That is, the unbeliever takes full responsibility for his choice. “Unbelief is not a misfortune to be pitied; it is a sin to be deplored.” The unbeliever’s sin lies first in his intentional refusal to believe God’s testimony about his Son and second, in his arrogant denial that the Father and the Son are one. Man cannot say that he has faith in God and at the same time reject God’s testimony about Jesus Christ.
Divine and Human Testimony (vv. 9–10)
John has outlined the nature of the testimony of God the Father to Jesus and is about to go on to summarize that testimony in order to provide a proper ending to the letter. But before he goes on, he pauses to show why the divine testimony should be believed. There are two reasons: First, it is greater than human testimony, which all people accept, at least at times; and second, willful unbelief is sin.
Verse 8 has introduced one important legal maxim into John’s argument: the principle that a point of fact is to be established by the agreeing testimony of two or three witnesses. Here he introduces another: the principle of character in a witness. This is obviously an important principle in any system of law, but it was particularly important in Judaism where it took the form of a listing of those who were by reason of their professions or questionable actions unqualified to bear testimony. In this list are found thieves, shepherds (because they seem to have let their sheep graze on other people’s land), violent persons, and everyone suspected of financial dishonesty including tax collectors and customs officials. The talmudic tractate Pesachim 49b contains a passage indicating that the people of the land, the ʿam hāʾāreṣ or common folk, were also excluded.
This principle is illustrated in John 8:14, in which Jesus says, “Even if I testify on my own behalf, my testimony is valid, for I know where I came from and where I am going.” Earlier, on the basis of the principle requiring two or three witnesses, Jesus had said that if he should bear witness to himself, his witness would not be acceptable (John 5:31). But here in John 8 he argues on the basis of the principle of character to say that if the witness of mere men is accepted, if corroborated by others, why should not his testimony be accepted for itself alone in that he is much more than a man? The rabbis rejected the testimony of unreliable men. They accepted the testimony of an upright man when substantiated by that of other upright men. Clearly they should accept the testimony of Jesus, who knows both his origins and his destiny, judges according to the truth and not after the flesh, as his opponents do, and works in perfect unity with God the Father.
This same approach is applied in 1 John 5, as John argues from our willingness to accept human testimony (which we all know is fallible) to our obligation to accept the testimony of God. Men and women accept the witness of other human beings every day of their lives. Otherwise they would not be able to sign a contract, write a check, pay a bill, buy a ticket, ride a bus, or do any of the other thousands of things that constitute daily living. Well, then, says John, why should they not believe God, whose word alone is absolutely trustworthy?
If a person does believe God, he has an internal assurance that what he has believed is trustworthy. This is the work of God’s Spirit, the testimonium internum Spiritus Sancti, as the Reformers termed it. It is in addition to the assurance provided on other grounds. On the other hand, if a person does not believe God, he makes him out to be a liar; for in this way he eloquently testifies to his belief that God cannot be trusted. Here the heinous nature of unbelief is evident, for, as Stott writes, “Unbelief is not a misfortune to be pitied; it is a sin to be deplored. Its sinfulness lies in the fact that it contradicts the word of the one true God and thus attributes falsehood to him.”
10 This verse summarizes John’s remarks on water and blood in a test that demonstrates whether one has the true witness that proceeds from God. If anyone believes in the Son of God, then that person “has the witness within herself” (NIV, “has this testimony in his heart”). Negatively, one may also conclude that if someone does not believe God (i.e., does not accept God’s witness about the Son), then that person “has made [God] out to be a liar.” The similarity of the latter conclusion to 2:4 suggests that those who do not accept the Spirit’s witness about Jesus show that they are members of the world, just like those who deny that they have sinned. Since the Spirit, water, and blood represent a unified testimony, God’s testimony about Jesus is not distinct from John’s testimony, especially since the Spirit is the source of John’s testimony (4:6). To “believe in the Son of God,” then, means to accept John’s word that the human Jesus was God incarnate.
What does it mean for the believer to “have this testimony in his heart”? Many commentators conclude that John is speaking of an inner experience that comes from the Spirit. Those who take this position understand the “testimony” to be “an inward work of the Spirit in the believer which confirms outward kinds of experience. If a person believes in the Son of God, he experiences or develops an inner conviction that what he believes is verified in practice” (Grayston, 140). Barker, 352, believes that the “testimony” is “faith itself” and a subsequent “forgiveness of sins and inward establishment of the love of God,” both of which are gifts given by the Spirit in the move from “believing” to “receiving” (cf. Stott, 82). While this view is reasonable, it seems to suggest that John’s witness about Jesus requires a special work of God to become credible—the very point John has attempted to refute in vv. 7–9 by stressing the harmony of the Spirit, the water, and the blood. Other commentators have sought to explain v. 10 in more natural terms. Marshall, 241, argues that this verse simply indicates that “to believe in the Son of God is to accept and keep God’s testimony,” while rejecting the Son means rejecting God as a liar. “It is inconsistent to profess belief in God, as John’s opponents did, and yet to disbelieve what God has said.” This reading limits God’s “testimony” to the inspired, prophetic preaching of the church, which preserved and propagated the true witness about Jesus.
As a third possibility, v. 10 may have both the natural and supernatural dimensions of faith in mind. Perhaps John does not distinguish these aspects of faith to the degree that they are distinguished in modern Christian theology. The most immediate parallel to the thought of v. 10 appears in 2:20–21, 27. The “testimony of God” here seems equivalent to the “anointing” mentioned in that passage, and both terms probably refer primarily to the orthodox belief in Jesus’ literal, sacrificial death (see comment at 2:20–21). At the same time, John’s dualism complicates the process by which this testimony may be accepted. Dodd, 131–33, points out that 1 John 5:6–12 closely parallels John 5:19–47, both in its language and in its appeal to the same dualistic framework. In John 5 Jesus discusses the value of different types of “testimony” about himself, including John the Baptist’s witness, the Scriptures, and the power God has given him to do signs. The Jews cannot accept this overwhelming evidence, however, because God’s word does not “dwell in you” (5:38). It would therefore be against their nature to believe in Jesus, no matter how strong the testimony. Similarly, although John’s Christology is supported both by God’s actions in the life of Jesus and by the Spirit’s continuing testimony in the church’s prophecy, the Antichrists cannot believe because God’s word is not in them. They therefore must belong to the same category as the Jews and the world. Those who do accept John’s witness, on the other hand, automatically demonstrate that they have God’s testimony in themselves, i.e., that they are in the same category as God (see Jn 6:44; 10:3–4). This would suggest that the initial act of faith, crossing over from the sphere of darkness to the sphere of light, is based on obvious public facts but also has a supernatural dimension. Unfortunately, John does not describe the mechanisms of this transformation as carefully as modern theologians might wish.
 Tozer, A. W., & Smith, G. B. (2015). Evenings with tozer: daily devotional readings. Chicago, IL: Moody Publishers.
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (p. 2324). Nashville: Thomas Nelson.
 Kistemaker, S. J., & Hendriksen, W. (1953–2001). Exposition of James and the Epistles of John (Vol. 14, pp. 356–357). Grand Rapids: Baker Book House.
 Boice, J. M. (2004). The Epistles of John: an expositional commentary (pp. 134–135). Grand Rapids, MI: Baker Books.
 Thatcher, T. (2006). 1 John. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Hebrews–Revelation (Revised Edition) (Vol. 13, pp. 495–496). Grand Rapids, MI: Zondervan.