1) WHAT DOES THE MITZVAH OF "KIBUD AV" REQUIRE FROM A PERSON?
OPINIONS: The Beraisa teaches the source for the law that when the father of a Kohen tells his son to become Tamei with Tum'as Mes, or not to return a lost object, the son should not listen to his father. The Beraisa derives this from the verse, "Every man shall revere his mother and his father, and keep My sabbaths; I am Hash-m your G-d." (Vayikra 19:3). This verse teaches that "Kulchem Chayavim bi'Chvodi" -- "All of you are obligated in My honor," and thus Hash-m's command overrides the will of one's parent.
The Gemara implies that if not for this verse, the son would be obligated to listen to his father and not return the lost object. Does this mean that every request of a parent, even if it does not benefit the parent, is considered fulfillment of the Mitzvah of Kibud Av?
(a) TOSFOS in Kidushin (32a, DH Rav Yehudah) explains that in the case of a father who tells his son not to return a lost object, the father tells his son to serve him instead of returning the lost object. Tosfos says that if the father tells the son not to return the object for no reason, it would be obvious that the son does not need to listen to his father, and the verse indeed would not be necessary. Apparently, Tosfos understands that the Mitzvah of Kibud Av applies only when the father receives some benefit. This is also the opinion of the RAMBAN, RASHBA, and RITVA.
(b) The RITVA in Yevamos (6a) understands that RASHI there (DH Hitamei) maintains that even when a father makes a request of a son which provides no benefit to the father, the son is obligated to obey because of the Mitzvah of Kibud Av.
(c) The RASHBA in Yevamos seems to have a third opinion. He writes that when a parent commands a child to do something which does not benefit the parent, "this is not considered Kibud Av which the son is commanded to fulfill, and this type of Kavod has no Mitzvas Aseh which would override even an ordinary Lo Ta'aseh." The BI'UR HA'GRA (YD 240:36) writes that the Rashba implies that there is a Mitzvah to fulfill the father's request in such a case, but it is not the type of Mitzvah which overrides a Lo Ta'aseh. The CHAZON ISH (Kidushin 32a) understands that the Rashba may understand that this is even a Torah obligation. (Y. MONTROSE)
2) THE SOURCE FOR "TZA'AR BA'ALEI CHAYIM" IN THE TORAH
OPINIONS: According to one opinion in the Gemara, the precept of "Tza'ar Ba'alei Chayim" is a Torah prohibition. What is the source for this?
(a) The RITVA and RABEINU PERETZ understand that this opinion maintains that "Tza'ar Ba'alei Chayim" is a Halachah l'Moshe mi'Sinai.
(b) The SHITAH MEKUBETZES quotes the RA'AVAD who says that this law may be derived from the prohibition against muzzling an ox while it threshes (Devarim 25:4), which teaches that one may not cause pain to an animal.
(c) RASHI in Shabbos (128b, DH Tza'ar Ba'alei Chayim) explains that this opinion understands that the prevention of pain to an animal is the reason behind the Mitzvah of Perikah (Shemos 23:5), unloading an overburdened animal.
The RAMBAN (33a) asks that according to the opinion that "Tza'ar Ba'alei Chayim" is mid'Oraisa, why does the Torah exempt a Zaken (a Torah scholar) from the Mitzvah of Perikah?
1. The Ramban answers that the Torah deems that upholding the honor of the Torah takes precedence over preventing pain to an animal.
This answer suffices only according to the Rishonim who understand that a "Zaken" is a Torah scholar. Other Rishonim (see Insights to 30b) maintain that a "Zaken" refers to anyone for whom such an act is below his dignity. According to those Rishonim, why is a Zaken exempt from Perikah?
2. The RAN answers that an exception to the prohibition of "Tza'ar Ba'alei Chayim" is where man will benefit. Indeed, the REMA (EH 5:14) explicitly rules that any benefit to man (which is deemed a necessary benefit) overrides the prohibition of "Tza'ar Ba'alei Chayim." Similarly, the necessity for a man to maintain his dignity is considered a necessary benefit, and therefore it overrides the concern for the animal's suffering.
The MINCHAS CHINUCH (#80) utilizes this idea to explain the Gemara which says that when one is faced with the choice of helping his friend unload his animal or helping his enemy load his animal, he should choose to help his enemy load his animal. The Gemara asks that making the suffering animal of his friend wait is considered "Tza'ar Ba'alei Chayim," and thus he should unload his friend's animal first. The Gemara answers that it is more beneficial for him to subdue his Yetzer ha'Ra by helping his enemy first. Why, though, should the animal suffer as a result of one's desire to work on his Yetzer ha'Ra? The Minchas Chinuch explains that since "Tza'ar Ba'alei Chayim" is suspended for the needs of man, there is no greater need of man than to defeat his Yetzer ha'Ra. (Y. MONTROSE)