What does it mean to exhort one another while it is still called today (Hebrews 3:13)?

Such being the case, how urgent is the warning of verse 12: "Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God," (or "in falling away from the living God"). He is not speaking of weakness of faith or of failure in details of conduct, but of an evil heart of unbelief, faith not being present at all. This is the cause of falling away, a fall into a state of cold rejection of One previously acknowledged as the Son of God. Only faith can maintain this position of firm confidence in the blessed Son of God; so that a mere lip profession that lacks this vital root of the matter, may very soon give place to a callous reaction of deliberate apostasy, from which there is no recovery: the living God is rejected, and the only alternative is the cold, cheerless state of death.

"But exhort one another daily, while it is called Today; lest any of you he hardened through the deceitfulness of sin." If in the case of those truly born again, this ex­hortation would stimulate and encourage their faith, it might also, in the case of any who lacked faith, be the means of awakening and bringing them in reality to the Lord Himself, and thus prevent so dreadful a fall. For sin will harden, however innocent its face may at first appear; and those deceived by it will choose eventually to mock at faith. The expression "while it is called today" insists that the present is the time of testing, which may abruptly end at any moment.

παρακαλέω (καλέω, 'to call'), which it is difficult to render in any uniform way, is calling upon a person in order to stimulate him to something, it may be to comfort; but it often refers to other things — to exhortation in general, as in Rom. 12:8; Titus 2:15; and in some passages may well be translated 'encourage,' as in Heb. 3:13, "Encourage one another daily," also in Heb. 10:25. See 2 Cor. 1:3-7 where the word, with the substantive formed from it, occurs several times with a more active force than 'comfort.' In Acts 4:36 the name Barnabas, υἱὸς παρακλήσεως, should probably be 'son of exhortation' rather than 'of consolation.'

This danger they were to remember, and real care for one another was to be aroused, evinced, as it would be, when in exercise, by exhorting one another, whilst the time was the time of to-day. Each one, however, should have no doubt about his own salvation, and so be free to watch over in that respect the interests of his brethren. Evidently to no special class among them was this duty delegated. Elders there were at Jerusalem (Acts 15:6, 21:18). This charge, however, was not entrusted to them. Saints, brethren in Christ, children of the Father, sons of God — these were to care for one another and to exhort one another day by day. The deceitfulness of sin was to be remembered, its hardening process feared. A danger this was to which any might be exposed, and which could only he effectively resisted by watchfulness, and, may we not add? by prayer. Besides, however, the danger to be avoided, there was a favour to be enjoyed, though in its fulness to be known only in heaven. We refer to that which follows: "For we are made [or, become] partakers [rather, fellows] of Christ, if we hold the beginning of our confidence steadfast to the end; while it is said, To-day if ye will hear His voice, harden not your hearts, as in the provocation" (Heb. 3:14-15).

We are warned therefore against an evil heart of unbelief which departs from the living God, and bidden to exhort one another daily for sin is very deceitful. If believers are to exhort one another daily it means that daily they seek one another's company. This verse then takes for granted that, like the Apostles who, "being let go … went to their own company" (Acts 4:23), we also find our society and companionships amongst the people of God. It also infers that we watch for one another's souls and care for one another's spiritual prosperity. But is this true of us all? The general spiritual health of Christians would be much better if it were. We are far more influenced by the company that we keep than many of us like to admit.

If however, any of us have professed the name of Christ without reality, then there is still in us the evil heart of unbelief, whatever we may have said with our lips; and the downward course that lies before us, except we be awakened to realities, is plainly set before us. The evil heart of unbelief is easily deceived by sin; and sin itself by reason of its deceitfulness hardens us, so that we become impervious to reproof. Then instead of holding "the beginning of our confidence stedfast to the end," we let go and give up. But only the real, who do remain stedfast to the end, are made partakers, or companions of Christ.

The word is addressed to them severally: "lest any of you," etc. But incessant mutual exhortation is the instrument which God has ordained for the maintenance of practical faith and godliness among His saints. It was to be a remedy of daily use. While the day of patience lasted, they were thus to succour one another from the deceitfulness of sin. It is not open evil that is spoken of, but the slow, imperceptible waning of the soul's affections from the living God; the gradual induration of those hearts which, when nourished by the sure milk of the word, were soft and tender in the sweet enjoyment of the love of Christ. They were to care thus for one another's souls, as already they had proved their forwardness in ministering to their brethren's outward wants.

(Vv. 12, 13). In these verses the warnings of Psalm 95 are applied to professing Christians. We are to “take heed” lest, through an evil heart of unbelief, we turn away from the living God to put once again our confidence in dead forms, thus showing that, whatever profession may have been made, the soul has no confidence in Christ and the grace that, through His finished work, secures to the believer salvation and forgiveness. However, what is contemplated is hardly the adding of Jewish forms to the Christian life, bad as this is, but the giving up of Christ altogether and turning back to Judaism, which is apostasy.

Further, we are not only exhorted to take heed to ourselves but to “exhort one another” each day, while it is still a day of grace and salvation, lest any be hardened by the deceitfulness of doing one's own will. Here it is not the deceitfulness of committing sins, solemn as this is, for one sin leads to another: it is the principle of sin of which the writer speaks, which is lawlessness. We little think how we harden our hearts by doing our own will. We are thus to take heed to ourselves and care for one another. Love should not be indifferent to a brother slipping away by doing his own will.

That is the substance, briefly, of what we have in this portion. In the twelfth and thirteenth verses, the apostle applies this to the Hebrew Christians: "Take heed lest there be in any of you an evil heart of unbelief in departing from the living God." He is not warning against falling into some outward sin. Sin, as occasionally mentioned in this epistle, is not immorality, not overt acts of wickedness, but the radical sin that produces all other sin. It is that evil heart of unbelief in departing from the living God. Unbelief is the source from which flows every form of sin. So in speaking to professors, what he warns them against is turning away from the living God and giving up Christ. This is the sin into which they are in danger of falling. He says, Take heed, if you want your praises to continue, if you want to go through this wilderness journey with joy in your soul, that you do not depart from the living God; but rather exhort one another daily while it is called today. "Today," is whilst the Spirit invites, and continues to this present time. It is always "today" until we enter the bright "tomorrow" that is before us; and "while it is called today" we are to exhort one another lest any of us should "be hardened through the deceitfulness of sin."

And notice that expression "hardened." Sin is a thing that hardens — the heart and conscience becoming callous, less sensitive. In the joy of first love, Christ fills the heart, and any thought of giving Him up is torture to the soul. Oh, who with the joy of first love in his heart would think for a moment of turning from Christ to anything else? But the sin of unbelief hardens. If you turn away from Christ, if you allow the world to come in, or, as these Jewish Christians were allowing, persecutions on one side, and the desire to be identified with Judaism on the other, to come in between the soul and Christ — if these things come into the soul, the heart becomes hardened. The sin of unbelief is a deceitful thing. It detaches one imperceptibly from the object of faith, and, before you are aware of it, the result is grievous dishonor to Christ. If he is a true beliver, like Peter, thank God, he will be brought to repentance. If he finds that he has failed, out of the very ashes of failure and unbelief, God will bring in brightness again. The very overwhelming flood that God permits to come upon us, the crushing sense of humiliation and sorrow because of our failure, will be the occasion used of the Spirit of God to bring out again that faith which was losing its brightness. The very sorrow of our experience will be His means of restoring us to Himself. But as the apostle is speaking of profession, true and false as well, he shows the effect of sin upon the heart to make them careless and coldhearted; then to allow something else than Christ to have a place, until Christ loses value in the eye of the heart and they go back again to that Judaism, — to shadow instead of the substance; it becomes an idol now, in that it displaces Christ: they give up Christ. That is the deceitfulness of sin; and we, as true believers, need to exhort one another, not against doing this or that or the other thing merely, but to exhort one another daily to hold fast to Christ.

Verse 13. "While it is called to-day." It is "to-day" as long as the word of God is proclaimed, and there is a call on God's part; the judgment will be the close of this calling.

No one ought to harden his heart; but this word is especially addressed to Israel, and that until the day when Christ shall appear. In speaking of it, the author returns to the word that had formerly been addressed to Israel; not now in order to warn them of the danger they would incur by neglecting it, but of the consequences of departing from that which they had acknowledged to be true. Israel, when delivered out of Egypt, had provoked God in the wilderness (it was indeed the case also of Christians in this world), because they were not at once, and without difficulty, in Canaan. Those to whom he wrote were in danger of forsaking the living God in the same way; that is, the danger was there before their eyes. They should rather exhort each other, while it was still called to-day, in order that they might not be hardened by the deceitfulness of sin. This word "to-day" is the expression of the patient activity of God's grace towards Israel even unto the end. The people were unbelieving; they have hardened their hearts; they have done so, and will alas! do so to the end, until judgment come in the Person of the Messiah-Jehovah, whom they have despised. But until then God loves to reiterate, "To-day, if ye will hear my voice." It may be that only a few will hearken; it may be that the nation is judicially hardened, in order to admit the Gentiles; but the word "to-day" still resounds for every one among them who has ears to hear, until the Lord shall appear in judgment. It is addressed to the people according to the long-suffering of God. For the remnant who had believed it was an especial warning not to walk in the ways of the hardened people who had refused to hearken — not to turn back to them, forsaking their own confidence in the word which had called them, as Israel did in the wilderness.

As long as the "to-day" of the call of grace should continue, they were to exhort one another, lest unbelief should glide into their hearts through the subtlety of sin. It is thus that the living God is forsaken. We speak thus practically, not with reference to the faithfulness of God, who certainly will not allow any of His own to perish, but with regard to practical danger, and to that which would draw us away — as to our responsibility — from God, and for ever, if God did not intervene, acting in the life which He has given us, and which never perishes.

Hence the call to encourage, not exactly one another, though this is included, but "yourselves," which seems rather more pointed than the former phrase. They were to encourage each other day by day as long as it is called today (the day of grace), that none should be hardened by sin's deceitfulness. For which of us knows not by humbling and bitter experience its luring character and slippery paths? A little evil allowed is the beginning of very great evil. The heart is hardened as we look off from Jesus, and self-pleasing takes the place of doing God's will; and only mercy's intervention hinders the end from being, according to the way. Truly sin is deceitful.