Gemara

10b - Question: "(David) cried... my son Avshalom, my son, my son, Avshalom, if only I had died in your place..." Why did he say "my son" eight times?

Answer: Seven times were to save him from the seven chambers of Gehinom. Some say that the eighth was to get his head to rejoin his body. Others say, it was to bring him to the world to come.

14a: "For the sinners he prayed" - Moshe prayed that sinners of Yisrael repent.

Sanhedrin 104a - Question: Why isn't Amon listed among those who have no share in the world to come?

Answer: It is due to the honor of Yoshiyahu (his son).

Question: If so, also Menasheh should not be listed, due to his father Chizkiyah!

Answer: A son brings merit to his father, but a father does not bring merit to his son:

"V'Ein mi'Yadi Matzil" - Avraham does not save Yishmael (from punishment; this is according to the opinion that Yishmael did not repent), and Yitzchak does not save Esav.

Bava Basra 4a: Hordus tried to persuade Bava ben Buta (who did not know with whom he was speaking) to curse Hordus for killing the Chachamim

Bava ben Buta: One may not curse a rich person or Nasi - "u'Vchadrei Mishkavecha Al Tekalel Ashir", "v'Nasi v'Amecha Lo Sa'or".

Hordus: Hordus is not "Amecha", i.e. one who acts like one of your nation!

Bava Basra: Even though no one else is here, I fear him - "Ki Of ha'Shomayim Yolich Es ha'Kol".

Hordus regretted that he killed the Chachamim, and asked how to atone for this.

Bava ben Buta: You destroyed (Chachamim,) the light of the world - "Ki Ner Mitzvah v'Sorah Or." Go fix (the Mikdash,) the light of the world - "v'Naharu Elav Kol ha'Goyim".

Question: Why did Bava ben Buta give such counsel?

(Rav Yehudah): Daniel was punished for counseling the evil Nebuchadnetzar to redeem his sin through Tzedakah - "v'Chata'ach b'Tzidkah Feruk... Teheve Archah li'Shlevsach (and you will have serenity for a long time);

Answer #1: Hordus was a slave, who is obligated to keep the Mitzvos.

Answer #2: Only Hordus, the king, could rebuild the Mikdash.

Rosh Hashanah 16b (R. Avin): "Yimachu (the Resha'im should be erased) mi'Sefer" refers to the Sefer of utter Resha'im; "...Chayim" is Sefer Tzadikim; "and not written with Tzadikim" refers to Sefer Beinonim.

Bereishis Rabah (49:1 DH va'Shem): One who mentions a Rasha's name and does not curse him transgresses an Aseh - "v'Shem Resha'im Yirkav."

Rishonim

Rambam (Hilchos Rotze'ach 12:15): It is forbidden to give good counsel to a Nochri or Eved Rasha, even to do a Mitzvah, if he persists in his evil.

Kesef Mishneh: This is like the second answer, that Bava Basra counseled Hurdos only because no one else could rebuild the Mikdash.

Kovetz Shi'urim (Bava Basra 24): According to the second answer, it should be forbidden to give good counsel even to a Yisrael Rasha! We cannot distinguish, for even a slave is called "Achicha"! Perhaps the Rambam agrees; he mentioned 'slave' only because the Gemara discussed a slave.

Me'iri (Bava Basra 4a DH Kevar): Sometimes a Rasha sins so much that Hash-m takes away his ability to repent. If a Chacham or rebuker recognizes this, he should not give to him counsel to atone for his sin. This is why Daniel was punished. However, if the sinner is commanded in Mitzvos at least as much as women are, it is extremely rare that he would be in this category.

Ramah (Bava Basra 4a DH Ahadar): We learn from Bava ben Buta that one should not curse a rich person or Ashir, even if he angered Hash-m. "V'Nasi v'Amecha Lo Sa'or" exempts one who curses him, but it is forbidden due to danger, lest he find out.

Tosfos (Sotah 10b DH d'Aisei): In Sanhedrin, we say that a father does not bring merit to his son. We can say that since Avshalom was punished in this world (he suffered a cruel death), David's prayer helped for him. Alternatively, we do not list a son among Resha'im due to his father's honor only if his father prayed for him.

Acharonim

Yefe To'ar (on Bereishis Rabah): We conclude like Bruriyah, that it is improper to curse Resha'im (Berachos 10a). This refers to during their lives, for perhaps they will repent. "V'Shem Resha'im Yirkav" applies after they died.

Chida (Tziporen Shamir 183): One must be careful not to curse his wife, for she is part of him, so it is like cursing himself. One may not curse anyone (of Yisrael), for this is like cursing a part of Hash-m, i.e. blasphemy!

Question (Pnei Yehoshua Rosh Hashanah Sof 16b): How could David pray that they not be in any Sefer? Every person has his Sefer! And why did David pray that they be erased from Sefer Resha'im? And why does he request that they be erased from the Seforim of Resha'im and Tzadikim, and not written in Sefer Beinonim?

Answer #1 (Pnei Yehoshua): All of Tehilim 69 pertains to David's enemies, i.e. Doeg and Achitofel. They were awesome Chachamim. Only Sin'as Chinam (groundless hatred), which is equal to all the Aveiros, could outweigh the reward for their Torah. Hash-m's Midah is to remove the first sin. If this was Sin'as Chinam, they would be written in Sefer Tzadikim! Therefore, David prayed 'put sin on their sins', i.e. Sin'as Chinam should be put on the scale of Aveiros. If Hash-m would treat them like Beinonim, He would lean towards Chesed (and they would be with Tzadikim). However, David did not want Hash-m to treat them like utter Resha'im, who receive their reward in this world to deprive them of the world to come, lest they succeed against him.

Answer #2 (Aruch l'Ner 16b DH Zeh): We find that the generation of the flood has no share in the world to come, nor was it judged, i.e. it was not in any of the three Seforim! David knew that it would be best for these Resha'im not to be punished, just like it was decided that Acher neither get the world to come nor be judged (Chagigah 15b). Also Moshe requested for himself "Mecheni Na", as if he never was!