Kabbalah for Daniel 12:1

We have learned that the gathering of the exiles preceded the raising of the dead by forty years, as it is written, "And Isaac was forty years old." What is to be made of these forty years? According to Rav Kahana, Rabbi Broka said, How many troubles, how many wars waged against the children of Yisrael will there be from the gathering of the exiles until the resurrection of the dead. He who escapes them is happy, as it is written, "And at that time your people shall be delivered, every one who shall be found written in the book" (Daniel 12:1). Rabbi Yehuda said that this teaches us, "Many shall purify themselves, and make themselves white, and be tried" (Ibid. 10). Rabbi Yitzchak added, "and will refine them as silver is refined, and will try them as gold is tried" (Zecharyah. 13:9). During these very days, there will be days when people will say, "I have no pleasure in them" (Kohelet 12:1). And from the time the troubles disappear until the resurrection of the dead there will be forty years.