God created the universe in such a way that we have both day and night. The principle is the same in our spiritual experiences: we have both nights and days. The experience described in Numbers 25 was in the night, but in Numbers 26 we have something related to the day.
Chapter twenty-six is devoted to the renumbering of God's people.
The renumbering in chapter twenty-six took place immediately after the purification by the plague on the fornicators and idolaters (v. 1a). The failure in chapter twenty-five was the greatest failure of God's people in the wilderness. This is proved by the fact that twenty-four thousand people died by the plague (25:9). This plague was a purification of God's people, and this purification was a sifting that dealt with the mixture among them.
Numbers 11:4 speaks of "the mixed multitude." This indicates that among the congregation of the children of Israel there was a mixture. Some impure ones had become mixed with the people of God.
Since the history of Israel is a complete type of the church, the mixture among the children of Israel is a type of the mixture in the church. There will often be some kind of mixture in the church life. Even with the apostles chosen by the Lord Jesus there was one—Judas—who was not pure. Acts 5 indicates that, at the very beginning of the church life, there was mixture in the church in Jerusalem. The mixture there was with Ananias and Sapphira, who were genuine believers but were not pure. Furthermore, the last of the epistles written by Paul, 2 Timothy, has much to say concerning mixture. Some, like Alexander the coppersmith (1 Tim 1:20; 2 Tim. 4:14-15), hated Paul and opposed him to the uttermost. Many of those in Asia who had been raised up by Paul turned away from his ministry (1:15), and Demas, a co-worker, because of his love for the present age, forsook Paul (4:10). The point here is that there is mixture among God's people, and God uses the failure and turmoil among His people to purify them.
After the great failure in Numbers 25, the children of Israel were purified. The punishment in chapter twenty-five was the last purification of the children of Israel before they entered into the good land. The twenty-four thousand who were killed by the plague should have included some of those who had been condemned for their failure in chapter fourteen. Those who survived all the purifications in the wilderness, especially the last and greatest purification, were a purified people. These purified ones needed to be renumbered.
This renumbering implies some amount of replacement and re-formation. There was the need to replace all those in the army who had died. Also, there was the need for the army to be re-formed. From this we see that the renumbering was very significant.