The following is from the text “Derech Hashem” (The Way of G-d) by Rabbi Moshe Chaim Luzzatto (RaMChaL). Derech Hashem is a systematic exposition of Torah fundamentals explaining basic beliefs regarding the existence of G-d and His purpose in creation.
The rule that the Community of the Future World [Olam Haba] is restricted only to those who attained perfection in their own right is not absolute. For it was also decreed that an individual can reach a level where he can partake of perfection and be included in the Community as the result of his association with a more worthy individual. The only difference is that he will remain on a lower level, since he is not included in the Community in his own right, but only through the association of another.
The only ones who are cast aside completely from perfection, therefore, are those who are not worthy of it at all, neither through their own merit nor through the association with another. Because of this, the number who are saved from annihilation and allowed the ultimate bliss is maximized.
Those who cause others to partake in the World-to-Come will definitely be the foremost in the Community. They will be the leaders, while those who enter by virtue of their association with them will be beholden and dependent on them.
In order for this to be possible, all men were originally bound to each other, as our Sages teach us, “All Israel are responsible for one another.” As a result of this, each individual is bound to everyone else, and no man is counted separately. Hashem’s Attribute of Good is the stronger, however, and if the guilt for sin is shared by others, this must certainly be true of the merit associated with good deeds.
As a result of this principle, suffering and pain may be imposed on a tzaddik ( righteous person) as an atonement for his entire generation. This tzaddik must then accept this suffering with love for the benefit of his generation, just as he accepts the suffering imposed on him for his own sake. In doing so, he benefits his generation by atoning for it, and at the same time, is himself elevated to a very great degree. For a tzaddik such as this is made into one of the leaders in the Community of the Future World, as discussed earlier.
Such suffering also includes cases where a tzaddik suffers because his entire generation deserves great punishments, bordering on annihilation, but is spared via the tzaddik’s suffering. In atoning for his generations, through his suffering, this tzaddik saves these people in this world, and als greatly benefits them in the World-to-Come.
In addition, there is a special, higher type of suffering that comes to a tzaddik who is even greater and more perfected than the ones discussed above. This suffering comes to provide the help necessary to bring about the chain of events leading to the ultimate perfection of mankind as a whole.
According to the original plan, the sequence of worldly events required that man undergo at least some suffering before both he and the world could attain perfection. This was required by the very fact that one of the basic concepts of man’s predicament was that Hashem should hold back His Light and hide His Presence. This became all the more necessary as a result of the corruption and spiritual damage caused by man’s many sins, which held the good back even more and caused Hashem’s presence to become all the more hidden. The world and everything in it are therefore in a degraded evil state, and require that Hashem’s unfathomable wisdom bring about numerous chains of events to achieve their rectification.
Among the most important elements of this sequence is the requirement that man be punished for his wickedness until the Attribute of Justice is satisfied. Hashem arranged matters, however, so that select perfect individuals could rectify things for others, as discussed earlier. The Attribute of Justice therefore relates to them rather than to the rest of the world in general.
Individuals such as these, however, are themselves perfect, and are therefore worthy only of good. The only reason that they suffer is because of other, and the Attribute of Justice must therefore be as satisfied with a small amount of suffering on their part as with a large amount on the part of those who actually sinned.
Beyond that, the merit and power of these tzaddikim is also increased because of such suffering, and this gives them even greater ability to rectify the damage of others. They can therefore not only rectify their own generation, but can also correct all of the spiritual damage done from the beginning, from the time of the very first sinners.
It is obvious that individuals such as these will ultimately be the foremost leaders in the Perfected Community, and the ones who are the very closest to Hashem.
All this is not only the result of justice, but also follows from the actual order of things. As a result of man’s sins, corruption is increased and incorporated into both man and the world. This in turn causes Hashem’s Light to be increasingly retracted and hidden. The more that this corruption is cleansed, on the other hand, and the more people that are purified of it, the more Hashem’s Light is once again revealed, step by step.
Suffering is the thing that Hashem created to cleanse the pollution, both in general and in particular. Thus, through the suffering of these select individuals, creation in general is cleansed, and step by step the world is brought closer to perfection.
. Zohar 3:220b, Tikkunei Zohar 32 (76b), that Tzaddikim enter Gehinom to help others leave. Cf. Anaf Yosef on Tanchuma, Vayeshev 3, and Zohar Chadash 25a. This is even true of those who the Talmud says have no portion in the World-to-Come. They can still share the portion of a Tzaddik: cf. R. Bachya on Vayikra 18:29, quoted in Shikchas Leket (in Yalkut Reuveni, Warsaw 5644) 217a, s.v. Mah; quoted in Ta’amei ha-Minhagim, Kuntres Acharon § 536 (p.232). Also see Ramasayim Tzofim 15 on Tana D’vei Eliyahu Rabbah (p. 64a). Also see Kesubos 111b
. Shavuos 39a, Sanhedrin 27b, Sifra and Rashi on Vayikra 26:37. Also see Shabbos 55a, Vayikra Rabbah 4:6, Tana D’vei Eliyahu Rabbah 11 (66b); Mechilta on Shemos 19:6. Reagrding the logic that people should be able to help each other spiritually for this reason, see Sotah 37b, Rashi as loc. S.v. Amar Rav Mesharshia. We also find that because of this mutual responsibility, one person can sometimes fulfill the responsibility of another, cf. Rashi, Rosh Hashanah 29a, s.v. Af Al Pi; Ran ibid. (on Rif 8a), s.v. Tani; Ran, Pesachim (on Rif 27b), s.v. Sheyuchal; Magen Avraham 167:40.
. Nega’im 2:1; Bertinoro ad loc. s.v. Beis; Bava Metzia 84b; Yerushalmis Berachos 2:8 (20a), Bereshis Rabbah 33:1, 44:6, Vayikra Rabbah 2:5; Shir ha-Shirim Rabbah 6:6, Koheles Rabbah 5:14, Pesikta 30 (191a), Zohar 165a, 167b, 1:180a, 2:10b, 2:36b, 2:53a, 2:195a, 2:212a, 2:269a, 2:257a, 3:17b, 3:38a, 3:46b, 3:118a, Sefer Chasidim § 528. Cf. Shabbos 139b, Sanhedrin 39a, Zohar 3:20b, 3:115a. Ramban on Shemos 32:32, Ikkarim 4:13. We thus find that the death of the righteous atones for the sins of their generation: cf. Shabbos 33b, Mo’ed Katan 25a, 28a, Yerushalmi Yoma 1:1 (2a), Shemos Rabbah 35:4, Vayikra Rabbah 27:7, Pesikta 27 (174b).
. Rabbi Shimon thus said that he could rectify the entire world from the time of creation, and therefor he also attained a highest level in the Future World: Sukkah 45b, Maharsha ad loc., Yerushalmi Berachos 9:2 (65a), Avos d’Rabbi Nasan 16:4, Eruvin 65a top, Sefer Chasidim § 611. Cf. Yoma 38b, Chagigah 12b, Mechilta on Shemos 15:1, Bereshis Rabbah 75:11; Tanchuma, B’shalach 10, Nitzavim 2. Also see Ta’anis 8a from Yeshayahu 64:4; Menoras ha-Maor 5:3:1:2 (299). Cf. Daniel 12:3, Rashi as loc.; Tanchuma, Noach 7; Berachos 17b, Ta’anis 24b, Chullin 26a, Yerushalmi Ma’aser Sheni 5:5 (35a); Ta’anis 21b, Bava Metzia 85a, Sanhedrin 114a.
. Cf. Bereshis Rabbah 19:7, that the sins of mankind caused the Shechinah (Divine Presence) to depart from the world, whereas the righteous were able to bring it back.