זוהר בראשית — דף קפז ע”ב

The Zohar explains that one who deprives himself of the good of the world to come has an incomplete soul. Rabbi Ḥiya asks about a perfect righteous man who did not merit children; Rabbi Yose answers that his deeds and the Torah protect him in the other world. Rabbi Yitzhak cites “to the eunuchs who keep My Sabbaths” and the promise of “a monument and a name better than sons.” The question of levirate marriage follows: the widow requires it, since it is not known whether the deceased was perfect in his deeds, and the Holy One, blessed be He, reserves a place for him until the righteous man dies, as in “until the death of the high priest.” Children are granted to the righteous at their death. God plants trees and, if they do not succeed, uproots them and plants them again. Then come “I praised the dead” and “better than both is he who has not yet been.”