Take heed, brothers, lest there be in any of you an evil heart of unbelief, in departing from the living God.
In Scripture the "heart" expresses the whole spiritual nature of man — his mind or understanding, his feelings and passions, his spiritual being, his will. Under sin the heart's thoughts are darkened, its passions degraded, its will perverted (Jeremiah 17:9; Ezekiel 11:19; Ecclesiastes 8:2). Accordingly, the gospel deals first and above all with the heart. Mere change of life, while a deceitful heart remains, will avail nothing. The gospel's first promise, therefore, is (Ezekiel 37:26, 27). The renewed heart implies everything — new light to the darkened mind, a renewed will, a new life. The root of all the evils that afflict our race is the unbelieving heart. You will find many urge in those days that, as faith is simply belief in testimony, as to whose value people may differ, unbelief is no sin. For instance, you may hear that a certain event took place in London last week, and the evidence seems to you so good that you believe the report; a friend of yours, however, does not believe it, because he thinks the evidence untrustworthy. In neither case does moral blame attach to the person; all that can be said is, that the two friends differ. Now any one who reads Holy Scripture will soon discover that, as to the great truths of religion, Scripture treats faith in them, or unbelief, in no such easy temper as this. Faith, according to the Bible, is our first duty, and unbelief a damning crime (Mark 16:16; John 6:29; John 3:18). What, then, is the essence of saving faith? (Romans 10:9, 10). It is believing God's testimony concerning His Son, concerning our doom as sinners, His love as our Saviour, His death for us, His resurrection, His reign over us, and His Spirit's work in us. As to God, it is our taking Him at His word, in all He tells us of our emptiness, and of Christ's fulness. As to ourselves, it is the assertion and triumph of the higher nature within us over the lower, of the unseen and eternal over the world of sense about us and within us. We see, then, why faith saves. It lays hold upon God; it overcomes the world. The believer lives as seeing Him who is invisible, as in presence of things eternal. God has clearly revealed to us this unseen lie, and established by many infallible proofs both its existence and its awful character. Reason deals with the evidence, and then, assured of the facts, faith's eye gazes upon them as though they were visible, and the believer lives under the abiding sense and power of them. What this power is, we see in Hebrews
11. Whereas, where an evil, unbelieving heart is, there will be found the victory not of faith, but of the world — evil thoughts, evil desires, evil words, evil acts, the deceitful heart desperately wicked. In Romans 1:28-32 we have one of the reasons why unbelief is condemned. It is a sin against knowledge. It may be said, indeed, that many live in ignorance of unseen realities; but whence springs this? With multitudes, from indifference. They care for none of the things that make for their soul's peace, and hence take no pains to know God's way of peace for guilty sinners. Multitudes, again, are lost by procrastination. The longer the delay, the less the hope. Worldliness grows upon one, deadness of heart spreads and deepens; ossification, stoniness of heart — the truest and most awful mortification known to us; the conscience becomes dulled, the eye of sense opens, the objects of sense allures, faith's eye closes, and unseen things become dim, shadowy, unsubstantial. Luxuries become, from habit, necessities; the lust of the flesh, &c., grow by indulgence; and the desires after better things unseen dwindle by disuse. Faint wishes after heavenly things, and these but seldom take the place of settled purpose; while the strong will, every day stronger, drags down the captive spirit to earth, and sense, and sin. Pride unites with careless indolence in making the unbeliever reject the gospel. He rebels against its simplicity. His good name, good works, good character — something of self as are equivalent for salvation; whereas, all the while, eternal life is God's free gift, which can neither be bought nor bribed, but must come of God's own rich, undeserved grace, for His Son's sake. Strange, too, as it may seem, the evil heart betrays its presence as much by shame as by pride; but it is the false shame, which springs not from sin but from fear of the opinion of the world about us. There is but one way to God, but there are a thousand ways of departing from Him. He who is the slave of impure thought, of anger, hatred, malice, envy, or covetousness, will find that his evil begirt will soon open up a way by which he may depart still further from the living God. To each and all the gospel says — Return. The test of faith is obedience.
Parallel VersesKJV: Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.