Of the testimony of God makes him a liar, and is a sin of the greatest enormity. It is the work of a depraved and guilty heart; for no one without this bias could reject the abundant witness God furnishes of the truth of his word, Ps 14:1. Especially is unbelief towards an offered Savior an unspeakable crime, justly sealing the condemnation of him who thus refuses to be saved, Joh 5:18; 1Jo 5:10.
UNBELIEF or INFIDELITY is a want of credence in the word of God; or it may be defined, a calling in question the divine veracity, in what God hath either testified, promised, or threatened; and thus it is the opposite of faith, which consists in crediting what God hath said, Joh 3:18,33. It is said that the Jews could not enter into the promised land, "because of their unbelief," Heb 3:18-19. And the Apostle, teaching the believing Hebrews what instruction they should deduce from that portion of the history of their forefathers, says, as the words literally translated would run, "We are evangelized as well as they were; but the word which they heard did not profit them, not being mixed with faith in them that heard it," Heb 4:2. The meaning is, We Christians are favoured with the good news of the heavenly rest, as well as Israel in the wilderness were with the good news of the earthly rest in Canaan; but the word which they heard concerning that rest did not profit them, because they did not believe it. Hence it appears that faith and unbelief are not confined to the spiritual truths and promises of the Gospel of Christ, but respect any truth which God may reveal, or any promise which he may make even concerning temporal things. It is a crediting or discrediting God in what he says, whatever be the subject. Christ could not do many mighty works in his own country, because of their unbelief, Mt 6:5-6; their mean opinion of him, and contempt of his miracles, rendered them unfit objects to have miracles wrought upon or among them. The Apostles' distrust of Christ's promises, of enabling them to cast out devils, rendered them incapable of casting one out, Mark 17:16; and St. Peter's distrust of his Master's power occasioned his sinking in the water, Mt 14:30-31. The unbelief for which the Jews were broken off from their being a church was their denial of Christ's Messiahship, their contempt and refusal of him, and their violent persecution of his cause and members, Ro 11:20.
Adverting to the infidelity which prevailed among the educated class of Heathens when Christianity first appeared in the world, Dr. Neander observes: