Hebrews 3:19

So we see that they could not enter in because of unbelief.

The inspired author here defines and justifies his use of the word "today" in connection with his warning to all believers to remain steadfast to the end: in that it is said, Today when you hear His voice, harden not your hearts as in the provocation (at Meribah). Psalms 95:7. This present day is the time of which we may be sure; we know that the Lord's grace is being proclaimed to us now. It is now, therefore, that we should heed the Lord's warning and make the most of the present opportunity. For the dangers attending an insolent testing of God's patience are such as to make salvation a matter of chance and gambling: For some, having heard, yet provoked Him; was it not all that had gone forth from Egypt through Moses? Although all the children of Israel that went forth from Egypt heard the Word and will of God, yet they deliberately and maliciously challenged God's government and set about to embitter and provoke Him. And, unfortunately, there was not much choice among the rebellious people; they were all guilty of this provoking conduct, all the men that left Egypt under the leadership of Moses. It was not a case of having a few exceptional sinners to deal with, the whole mass of the gloriously rescued people whose faith had "carried them through between the threatening walls of water and over whom Miriam sang her triumphal ode," were in the same condemnation.

The sacred writer, drawing another lesson from the incidents in the wilderness, asks: But with whom was He angry, exasperated, forty years? Was it not with them that had sinned, whose bodies fell in the wilderness? It was not a matter of change of mind, of foolish caprice on God's part, nor was it lack of power to carry out His promise to the children of Israel. But their conduct provoked His anger, their sins challenged His punishment, the result being that all the men of twenty years and over that had left the land of Egypt sank into forgotten graves in the wilderness. That was God's punishment upon them because of their sin. The author, therefore, concludes his series of rhetorical questions by asking: And to whom did He swear that they should not enter into His rest unless it was to them that believed not? Not disobedience primarily, but unbelief, which was the cause of the various outbreaks against the Lord, caused the punishment to strike them. Moses freely and frankly told the people this very fact, Numbers 14:28. God finally affirmed with an oath that He would pour out His punishments, having the soundest reasons for vindicating His course of action. They did not reach the Land of Promise, they did not enter into the blessings of rest and peace which the Lord had promised to obedient, believing children. The conclusion of the sacred author emphasizes just this one point: And we see that they could not enter in on account of their unbelief. They could not reach their goal, the end of the way, because at the bottom of their entire unruly conduct lay the refusal to believe in the Lord, their God, with all their heart, with all their soul, and with all their mind. Their example should have its proper effect upon the Christians of all times. Every attention to sin with its deceitfulness, every shrinking from conflict in the interest of the Lord, endangers the faith, if it does not outright pluck it out of the heart. Our trust in God, to be of the right kind, must be centered in the promises of Scriptures and not permit itself to be moved from this foundation. There is too much at stake to make light of the matter or fatuously to rely upon a safe solution in the future. Today the Lord is calling; today we should give heed. To-morrow may be too late. Our Mediator is in every respect greater than Moses, but for that very reason we should cling to Him in all humility of heart.

Summary

The sacred writer, in showing the superiority of Christ over Moses, compares the two mediators, draws a warning lesson from the wilderness journey, and pictures the dangers of unbelief.