Hebrews 3:17

But with whom was he grieved forty years? - I believe it was Surenhusius who first observed that "the apostle, in using the term forty years, elegantly alludes to the space of time which had elapsed since the ascension of our Lord till the time in which this epistle was written, which was about forty years." But this does not exactly agree with what appears to be the exact date of this epistle. However, God had now been a long time provoked by that race rejecting the manifested Messiah, as he was by the conduct of their forefathers in the wilderness; and as that provocation was punished by a very signal judgment, so they might expect this to be punished also. The analogy was perfect in the crimes, and it might reasonably be expected to be so in the punishment. And was not the destruction of Jerusalem a proof of the heinous nature of their crimes, and of the justice of God's outpoured wrath?

Whose carcasses fell - Ὡν τα κωλα επεσεν· Whose members fell; for τα κωλα properly signifies the members of the body, and here may be an allusion to the scattered, bleached bones of this people, that were a long time apparent in the wilderness, continuing there as a proof of their crimes, and of the judgments of God.

But with whom was he grieved forty years? - With whom was he angry; see the notes at Hebrews 3:10.

Was it not with them that had sinned - That had sinned in various ways - by rebellion, murmuring, unbelief. As God was angry with them for their sins, we have the same reason to apprehend that he will be angry with us if we sin; and we should, therefore, be on our guard against that unbelief which would lead us to depart from him; Hebrews 3:12.

Whose carcasses fell ... - Numbers 14:29. That is, they all died, and were left on the sands of the desert. The whole generation was strewed along in the way to Canaan. All of those who had seen the wonders that God had done "in the land of Ham;" who had been rescued in so remarkable a manner from oppression, were thus cut down, and died in the deserts through which they were passing; Numbers 26:64-65. Such an example of the effects of revolt against God, and of unbelief, was well suited to admonish Christians in the time of the apostle, and is suited to admonish us now, of the danger of the sin of unbelief. We are not to suppose that all of those who thus died were excluded from heaven. Moses and Aaron were among the number of those who were not permitted to enter the promised land, but of their piety there can be no doubt; Beyond all question, also, there were many others of that generation who were truly pious. But at different times they seem all to have partaken of the prevalent feelings of discontent, and were all involved in the sweeping condemnation that they should die in the wilderness.