What is the difference between "Seivah" and "Zaken"?
Riva (citing R. Yosi, Kidushin 32b): Seivah is an old Chacham, and Zaken" is a Chacham, even if he is young. 4
Ramban, Targum Yonasan and Riva (both citing Isi ben Yehudah, Kidushin, 32b): One is obligated to rise and honor an old man - even if he is an ignoramus, 5 and a Chacham, even if he is young.
Riva (citing Tosfos): Abaye holds that one must stand for someone from whom he learned something, even if he is not a bigger Chacham. He expounds "Zaken" - Zeh she'Kanah Mimenu Chochmah.
Rashi implies that Zaken explains Seivah, i.e. an old Chacham. Riva - he must be 70 years old (Pirkei Avos, 5:21. It also says 'Ben Shishim l'Ziknah.' However, perhaps it means that it is the proper age to acquire Chachmah, just like 'Ben Chamesh l'Mikra
What does honoring a Zaken entail?
Rashi: It entails not sitting in his placeand not contradicting his words.
Why does the Pasuk add "Veyareisa me'Elokecha"?
Rashi: One might have thought that one may close his eyes, as if he did not see him, to avoid rising. 1 Therefore the Torah reminds us that Hashem is aware of his thoughts, even if nobody else is.
Moshav Zekenim #1 (from Kidushin 32b): This teaches that a Zaken should not unnecessarily cause the Tzibur to rise for him.
Moshav Zekenim #2: A Talmid is not Reshai (obligated 2 ) to show more honor to his Rebbi than to Hashem; he stands only morning and evening (just like he recites Shma only then).
Ibn Ezra, Moshav Zekenim: He will punish you in your old age (if you do not honor elders).
Moshav Zekenim #3: Hashem honors elders - "v'Neged Zekenav Kavod" (Yeshayah 24:23).
At what point does one stand for a Chacham?
Riva: It is when he is four Amos away, for then there is Hidur 1 (it is clear that he stands to honor him). However, for one's primary Rebbi, he stands when he is within sight.
Moshav Zekenim: If an elder is pained to stand, and you are sitting, it is Midas Chasidus to stand and tell him to sit. If he is not so old, and he can stand, it is honor him and and if he wants to sit - "v'Neged Zekenav Kavod" (Yeshayah 24:23).
Moshav Zekenim: Kimah and Hidur were taught together to teach that one stands in a way that shows honor. Also, one need not lose time from his work in order to stand, and one need not lose money in order to honor him. One is allowed to stop working in order to rise, unless he is working for someone else. One need not stand in a bathhouse or privy (it is not a place of honor).
Rashi writes that one might have thought that one may close his eyes, as if he did not see him. Do we discuss Resha'im?!
Riva (from Kidushin 33a): One might have thought that one may close his eyes before the Chacham comes within four Amos. The Torah says to fear Hashem, who knows that you seek to exempt yourself from His Mitzvos.
Rashi writes that one may not close his eyes to avoid seeing him. We permit scheming to avoid Mitzvos, e.g. one may enter grain into his house with the chaff, to be exempt from Ma'aser!
Moshav Zekenim citing Ri: Honor of the Torah is greater [than other Mitzvos, therefore here one may not scheme]. 1
This does not apply to rising for an old ignoramus. If so, one may scheme about this! (PF)
Rashi writes that "Zaken*" is a Chacham; we learn from "mi'Ziknei Yisrael" (Bamidbar 11:16). If so, this should apply only to people whose mothers' lineage was checked, like the Sanhedrin!
Moshav Zekenim citing R"Tz: It is a mere Giluy Milsa that we discuss Chachamim (they need not be literally like the Sanhedrin).