1) AN AGENT OF BEIS DIN WHO KILLS ACCIDENTALLY
OPINIONS: In the Mishnah, Aba Shaul states that the reason why the verse (Devarim 19:5) mentions that the accidental murderer went into the forest to cut down trees is in order to teach that the law of Galus for accidental murder applies only to a case in which the killer was not obligated to be in the situation which he was in at the time of the killing (such as two people who voluntarily went into a forest to chop wood). If, on the other hand, the killer was obligated by the Torah to be in that situation, then he is not required to go to Galus if he accidentally kills. Examples of this exemption include a father who was required to reprimand his son, a teacher who was required to reprimand his student (and, while hitting his son or student, he accidentally killed him), and a Shali'ach (agent) of Beis Din who accidentally killed someone.
Under what circumstances is a Shali'ach of Beis Din exempt from Galus for killing accidentally?
(a) RASHI learns that the Shali'ach of Beis Din is exempt from Galus when he was required to administer Malkus to a person who transgressed a negative commandment and, while he was giving the lashes, the transgressor died. Although Beis Din always estimates how many lashes the person can endure without dying (as described in the Mishnah later, 22a-b), in this case the transgressor was unable to endure the number of lashes that Beis Din thought he could tolerate. The agent of Beis Din is not obligated to go to Galus since he was merely carrying out the verdict of Beis Din. This is also the opinion of the RITVA and the RAMBAN (according to one explanation).
(b) The ME'IRI rejects this explanation. In the case that Rashi describes it is obvious that the Shali'ach of Beis Din does not go to Galus. The MA'ASEH ROK'EACH, ARUCH LA'NER, and others point out that the Mishnah later (22b) explicitly states that a Shali'ach who kills while administering a punishment of lashes is exempt from Galus. According to Rashi, why does the Mishnah here repeat this law? The Me'iri explains instead that the case is one in which a Shali'ach of Beis Din is beating someone who refuses to obey the summons of Beis Din. If the Shali'ach accidentally kills the recalcitrant litigant, he is exempt from Galus. This is also the opinion of the RAMBAM (Hilchos Rotze'ach 5:6).
(c) The MIRKEVES HA'MISHNEH and GUR ARYEH answer that Rashi does not mean that the person died while receiving the prescribed number of lashes. Rather, Rashi means that the Shali'ach, on his own accord, added more lashes than the number prescribed by Beis Din. Although he was not acting in accordance with the directive of Beis Din, he is exempt from Galus. The Mishnah later (22b) discusses a Shali'ach of Beis Din who thought he was administering the proper amount of lashes but was mistaken in his count.
These Acharonim point out that this is why Rashi writes specifically that the Shali'ach was administering "forty lashes"; Rashi means that the Shali'ach gave one more than the maximum number of thirty-nine lashes.
(The Mirkeves ha'Mishneh and Gur Aryeh mention that this is also the opinion of the RA'AVAD (Hilchos Rotze'ach ibid.). However, many Acharonim (SHOSHANIM L'DAVID, TORAH TEMIMAH, and others) maintain that the word "more" in the Ra'avad is a mistake, and that the Ra'avad actually understands the Gemara like the Ritva. This word is also missing from the Costa edition of the Ra'avad.)
This explanation in Rashi, however, is difficult to understand. If the Shali'ach intentionally gave extra lashes to the transgressor without permission of Beis Din, then he should be considered a murderer; if he accidentally killed the transgressor, then he should go to Galus! The ARUCH LA'NER explains that the reason why the Shali'ach is exempt from Galus must be that killing in such a way is worse than an accidental murderer and is considered like Karov l'Mezid (close to intentional). Since the Shali'ach's act of killing is considered Karov l'Mezid, he does not go to Galus. (The Aruch la'Ner understands that this is the view of the Ra'avad.) The Mishnah, however, lists this case of a Shali'ach together with the cases of a father and a teacher, who definitely are less culpable than an accidental murderer, and thus the case of a Shali'ach of Beis Din must be similar.
The CHASAM SOFER (Teshuvos OC #177), in his explanation of the Ra'avad, writes that in the case of the Mishnah the Shali'ach was mistaken with regard to the number of lashes he was supposed to administer. He therefore is considered less culpable than an accidental killer, since he was involved in the Mitzvah of fulfilling the verdict of Beis Din.
Based on this approach, the Mishnah later (22b) is necessary to teach that the Shali'ach is exempt in a different case. When the Shali'ach thought that the number of lashes that he was supposed to give was much higher, he relies on Beis Din's estimate (that is, his mistaken assumption of what that estimate was) and he proceeds to give additional lashes despite the fact that the recipient of the lashes appears to be very ill. Accordingly, he was giving the Malkus in fulfillment of the directives of Beis Din and he does not go to Galus if he kills accidentally. In contrast, when the Shali'ach sees that the transgressor is on the verge of death, one might have thought that he should ask Beis Din to reassess the transgressor's condition before he gives the last few lashes. If he does not ask Beis Din to reassess the transgressor's condition, perhaps he is considered an accidental murderer and should go to Galus. The Mishnah later therefore teaches that the Shali'ach in that case is also exempt from Galus, since his sole intention was to fulfill the command of Beis Din. (Y. MONTROSE)
2) A FATHER WHO ACCIDENTALLY KILLS HIS SON
QUESTION: The Mishnah here states that a father goes to Galus if he accidentally kills his son. The Gemara asks that this seems to contradict the previous Mishnah (8a) that states that a father is exempt from Galus if he accidentally kills his son, since he has a Mitzvah to discipline his son. How are these two statements to be reconciled? The Gemara answers that although a father is obligated to teach his son a trade (and to reprimand him if he is not listening or behaving properly), if he accidentally kills his son while teaching him a second trade, then he must go to Galus.
Why does the Gemara need to find such an odd case to reconcile the two statements of the Mishnah?
(a) The Gemara should answer simply that the Mishnah here refers to a situation in which the father is not educating the son at the time that he kills him, and therefore there is no reason to exempt him from Galus! (TOSFOS)
(b) Alternatively, the Gemara should answer that the Mishnah here refers to an adult son. A father has no obligation of Chinuch once his son reaches the age of 22 or 24 (see Kidushin 30a). The Gemara in Moed Katan (17a) states that a father who hits his adult son transgresses the prohibition of "Lifnei Iver Lo Siten Michshol," because he tempts his son to transgress the Torah prohibition against hitting one's father. Why does the Gemara not say that the Mishnah here refers to an adult son, while the previous Mishnah refers to a son who is still a child? (ARUCH LA'NER, SI'ACH YITZCHAK, and others)
(a) TOSFOS explains that the Gemara understands that the Mishnah here intends to state a blanket law which applies even when the father accidentally kills his son when hitting him for educational purposes. The previous Mishnah (8a) says that even when the father intentionally hit and killed his son, he does not have to go to Galus, because he was engaged in the Mitzvah of educating his son (albeit too harshly). This reason does not seem to apply in a case in which the son was walking in the forest without the father's knowledge and the head of the father's ax flew off and killed the son. The Gemara, therefore, is unsure as to exactly when the Mishnah maintains that the father is exempt from Galus.
(b) The SHULCHAN HA'MELECH (Hilchos De'os 6:10) answers that a father is allowed to hit his adult son, provided that he does so in order to teach him Torah and Mitzvos. The SEDEI CHEMED proves this from the Gemara in Sanhedrin (70b) which states that Bas Sheva, the mother of Shlomo ha'Melech, rebuked her son for his actions. It relates that she tied him to a pillar and oppressed him. Although the CHIDA (in one explanation) says that she only threatened to beat him, the Midrash Tanchuma states explicitly that she beat him with a stick. It is evident from there that a parent is allowed to beat his or her adult child for the sake of guiding him in Torah and Mitzvos. Accordingly, a parent who accidentally kills his child in such a case is exempt from Galus. Therefore, this cannot be the case of the Mishnah here.
The LEV SHOME'A argues that a parent is never allowed to hit a grown child. The Gemara does not give this case as an answer, because the Mishnah makes a blanket statement implying that sons of all ages are included in the law.
He cites support from the words of RASHI in Kidushin (30a) that a father may not hit his grown son even for the sake of directing him towards Torah and Mitzvos. Rashi explains that the Gemara there refers to a father who wants to hit his son for the sake of rebuking him, and nevertheless he is prohibited from doing so since the grown son might rebel as a result.
The Si'ach Yitzchak also maintains that a father may not hit his grown child. He says that for this very reason the Gemara does not explain that the Mishnah here refers to a father who hits and accidentally kills his adult son. By hitting his adult son, he transgresses a prohibition and thus is not entitled to go to Galus (like one who is "Karov l'Mezid"). (Y. MONTROSE)