John Calvin Commentary Hebrews 3:13

"but exhort one another day by day, so long as it is called To-day; lest any one of you be hardened by the deceitfulness of sin:" — Hebrews 3:13 (ASV)

He also pointed out the remedy, so that they might not fall into this wickedness, and that was to exhort one another. For since by nature we are inclined to evil, we need various helps to keep us in the fear of God. Unless our faith is occasionally raised up, it will lie prostrate; unless it is warmed, it will be frozen; unless it is roused, it will grow sluggish. He would have us then stimulate one another by mutual exhortations, so that Satan may not creep into our hearts and by his fallacies draw us away from God.

And this is a way of speaking that ought to be especially observed, for we do not fall immediately by the first assault into this madness of striving against God. Instead, Satan gradually approaches us artfully by indirect means, until he holds us ensnared in his delusions. Then indeed, being blinded, we break forth into open rebellion.

We must then meet this danger in due time, and it is one that is near us all, for nothing is more possible than to be deceived; and from this deception eventually comes hardness of heart. We therefore see how necessary it is for us to be roused by the incessant goads of exhortations. Nor does the Apostle give only a general precept that all should take heed to themselves. He would also have them be solicitous for the salvation of every member, so that they should not allow any of those who had once been called to perish through their neglect. He who feels it his duty to watch over the salvation of the whole flock so as to neglect no one sheep, performs in this case the office of a good shepherd.

While it is called today. He now applies what David said more particularly to his own audience, for he reminds us that the word today, mentioned in the Psalm, should not be confined to the age of David, but that it comprehends every time in which God may address us. As often, then, and as long as He opens His sacred mouth to teach us, this sentence should come to our minds: Today, if you will hear His voice. In the same way, Paul teaches us that when the Gospel is preached to us, it is the accepted time in which God hears us, and the Day of salvation in which He helps us (2 Corinthians 6:2).

Now, we must avail ourselves of this opportunity; for if through our sloth we allow it to pass by, we will later deplore its loss in vain. So Christ says,

Walk while you have the light;
shortly shall the night come (John 12:35).

The particle while, then, or as long as, intimates that the seasonable time will not continue always, if we are too slothful to follow when the Lord calls us. God knocks at our door; unless we open to Him, He will no doubt in His turn close against us the gate of His kingdom.

In a word, the groans of those who despise the grace offered to them today will be too late. Since, then, we do not know whether God will extend His calling to tomorrow, let us not delay. Today He calls us; let us immediately respond to Him, for there is no faith except where there is such a readiness to obey.