Gemara

R. Yochanan wanted to see the Kordina'ah Dinar. He did not let the moneychanger stand up for him.

R. Yochanan: Workers are not Reshai (allowed) to stand for Chachamim.

Question (Mishnah): (When people come bearing Bikurim), all workers stand for them, greet them and bless them.

Answer (R. Yochanan): Workers stand for people bearing Bikurim, but they don't stand for Chachamim.

Kidushin 32b: Rava was serving at a feast in honor of his son's wedding. Rav Papa and Rav Huna brei d'Rav Yehoshua stood up for Rava, but Rav Mari and Rav Pinchas did not. Rava was upset.

Rava: Do you think that you are Chachamim, but Rav Papa and Rav Huna are not?!

A similar episode occurred in which R. Yitzchak brei d'Rav Yehudah did not stand for Rav Papa.

33b (R. Eibo citing R. Yanai): A Chacham is not Reshai to rise for his Rebbi more than twice a day, morning and evening. Honor of one's Rebbi should not exceed honor of Hash-m. (We say Shema Yisrael only twice a day.)

Question (Beraisa - R. Shimon ben Elazar): "Zaken, you will fear" teaches that a Zaken should not cause that people will have to rise for him.

If others must rise only twice a day, they should do so! What is wrong if he makes them rise?!

Rather, we must say that they must rise every time he passes!

Answer: Really, people need rise only twice a day. Still, the Zaken should minimize how much they must rise for him.

(R. Elazar): Any Chacham who does not rise for his Rebbi is called wicked. He will not live long, and he will forget his learning.

R. Ilai and R. Yakov bar Zavdi rose for R. Shemen bar Aba.

R. Shemen: That was unnecessary! Firstly, also you are Chachamim;

Secondly, people engaging in Torah need not stand for those who learn it!

(R. Elazar): A Chacham may not rise for his Rebbi while he is learning.

Abaye would curse those who accepted R. Elazar's teaching.

Pesachim 22b (Beraisa): Shimon ha'Amsoni used to expound every 'Es' in the Torah (to include something). For "Es Hash-m Elokecha Tira," he found nothing to include (that should be feared like Hash-m). He retracted all his Drashos.

R. Akiva: "Es Hash-m Elokecha Tira" includes (fearing) Chachamim.

Rishonim

Rif and Rosh (Kidushin 14a and 1:55): R. Elazar taught that any Chacham who does not rise for his Rebbi is called wicked. He will not live long, and he will forget his learning.

Rosh (56): The Rif brought only R. Elazar's teaching, that a Chacham who does not rise for his Rebbi is called wicked. He did not bring R. Yanai's teaching that a Talmid is Reshai to stand only twice. He holds that R. Elazar argues, and the Halachah follows him; he did not limit how often one rises. Also R. Akiva equated awe of Chachamim to awe of Hash-m. If one receives the countenance of the Shechinah several times in one day, he must stand in awe (each time). This is why Rav Ashi (when he fixed the text of the Gemara) put R. Elazar's words after R. Yanai, to teach that he argues. The Gemara (says 'Amar R. Elazar', but it) did not say 'v'R. Elazar Amar' (like it usually does when the latter Amora comes to argue) because R. Elazar was not in the same generation as R. Yanai.

Note: Our text says that Eibo said this in the name of R. Yanai. It seems that in the Rosh's text, R. Yanai said this himself. Or, perhaps he assumes that this Eibo was the father of Rav (Rashi Sanhedrin 5a). Surely, the Eibo who taught a teaching in the name of Reish Lakish (Chulin 123a) was a contemporary of R. Elazar!

Rambam (Hilchos Talmud Torah 6:2): Workers need not stand for Chachamim while working.

Kesef Mishneh: The Rambam and Tosfos explain 'workers are not Reshai to stand' to mean that they are not obligated.

Rambam (6:8): A Talmid who always sits in front of his Rebbi is Reshai to stand for him only morning and evening, lest his honor exceed honor of Shamayim.

Rosh (Kidushin 1:53): Workers may not stand if they are working for others. Alternatively, we discuss people working for themselves. They are not 'Reshai', i.e. they are not obligated. In Erchin 28b, 'Reshai' means obligated. Abaye would stand when he saw the ear of Rav Yosef's donkey, for we hold that one who rides is like one who walks. Therefore, he was obligated to stand.

Ran (Chulin 16b DH Amar): Rashi explains that one working for others may not rise. This is why R. Yochanan did not let the moneychanger stand for him. If Reuven gave merchandise to Shimon to sell and share the profits, Shimon may not engage in his own work, for then he cannot oversee the store properly. The word 'Reshai' forced Rashi to say so. However, in Kidushin it connotes that the always applies even to one who works for himself. We learned from the Hekesh of rising to honoring that workers are not Reshai to stand for Chachamim. Perhaps also there it refers to one working for others. Since one is exempt when working for himself, he may not do so when working for others. If one were obligated when working for himself, he would be obligated when working for others. Others say that 'Reshai' means obligated. The Rambam explains like this. Perhaps even regarding one's one work he is not permitted. Since letter of the law he is exempt, if one will stand, it will seem that others (working for others - PF) disgrace Chachamim.

Mordechai (Kidushin 499): A Talmid Chacham is Reshai to rise for his Rebbi only morning and evening. R. Baruch says that this refers to one who is engaged in Torah. He may not rise and be Batel from learning more than morning and evening. This is like we say in Shabbos, that we cease learning for Kri'as Shma and Tefilah. Therefore, it is not difficult why Rav Yosef would stand when he heard his mother's footsteps, and R. Tarfon would bend (for his mother to step on him) whenever she wanted to go to her bed. The Gemara connotes that this could even be 100 times a day, even though honor of a Rebbi exceeds honor of parents. (I.e. they would do so whenever they were not learning, but they would not interrupt learning for this more than twice a day - PF.)

Mordechai (500): We find that Rava was upset that his Talmidim did not rise for him at the meal. It is difficult to say that they did not rise for him in the morning! The Ri explains that one rises only twice in the Beis Midrash or a covert place. In a place where it is disgraceful to the Rebbi, if the Talmid does not stand he is liable.

Rashba (1:144): Regarding a Talmid who is learning, presumably the Halachah follows Abaye, for he is Basra. It seems that the Rif holds like this. He brought only R. Elazar's teaching that a Talmid who does not stand for his Rebbi is called a Rasha. He did not bring R. Elazar's other teaching that a Talmid is not Reshai to stand while he is engaging in Torah. This shows that he holds that one is obligated.

Tosfos Yeshanim (33b DH Ein): It is astounding to say that one may not stand more than morning and evening. Will we say that in all the cases (of Rebbeyim who were upset that their Talmidim did not stand, the Talmidim had not stood for them in the morning?! Rather, 'not Reshai' means that he is not obligated.

Tosfos (Chulin 54b DH Ein): We can similarly explain (Kidushin 33b) 'a Talmid is not Reshai to rise for his Rebbi more than twice a day', i.e. he is not obligated.

Poskim

Shulchan Aruch (YD 244:5): A worker need not stand for Chacham while working. If he is working for others and wants to be stringent and stand, he may not.

Beis Yosef (DH Ein): Also Tosfos (33a DH Ein) and the Ran (Kidushin 13a DH mi'Kan) gave the Rosh's answers (about Reshai). The Tur brought both answers, for both apply. The Rambam holds like the second answer.

Question (Mishkenos Yakov, Sof Ki Tavo): What is Tosfos' (54b) proof from Kidushin? There, we can explain Reshai to mean permitted. More than twice is forbidden, lest he honor his Rebbi more than he honors Hash-m!

Answer (Birkei Yosef 244:8): Tosfos did not bring a proof from Kidushin. He merely said that also there, we can explain Reshai to mean obligated. We cannot obligate one to honor his Rebbi more than the honor Hash-m demands, but he may do more, just like one may accept Malchus Shamayim more than twice a day.

Question: It is improper if he will choose to honor his Rebbi more than Hash-m!

Answer (Birkei Yosef): To accept Malchus Shamayim one must have proper intent, like a voluntary prayer. There is no such obligation when rising for his Rebbi. This is why he does only the latter more twice. Tosfos Yeshanim needed to explain that Reshai means obligated due to the Sugya in Kidushin. Presumably, Mishkenos Yakov thought that Tosfos brought a proof from Kidushin. Tosfos Yeshanim is not so clear. Even if Reshai means obligated, since the Talmid was exempt, why was the Rebbi upset? One can answer this.

Note: Perhaps because their Rebbi was serving them and honoring them, they should have shown honor to him (lest it seem that he is the Talmid!), unless it were forbidden to do so.

Rema (242:16): Some say that one need not rise for his Rebbi more than morning and evening. This is in only in the Rebbi's house. Outside, where people do not know that he already rose for him, he must stand.

Beis Yosef (DH Kasav ha'Rambam): Tosfos concludes that this is only for Talmidim who live in the Rebbi's house. Others must stand even 100 times a day, lest others suspect them of not rising. Even in the Rebbi's house, if new people came, they must rise. The Mordechai (499) explains that a Talmid who is learning may not rise and be Batel from learning more than morning and evening. The Rambam explains like Tosfos. This is why he wrote 'who always sits in front of his Rebbi.' The Rosh says that the Rif rules like R. Elazar, and unlike R. Yanai. Also the Rashba rules like this.

Shach (36): Even though the Rambam, Tur and Poskim bring that one is not Reshai, the Rema explains that he is not obligated. Also the Bach and Semag say so.

Gra (53): The Rema rules like the Rif, who rules like R. Elazar.