Shabbos Daf 22 שבת דַף 22

Rav Kahana said: Rav Nassan bar Manyumi expounded in the name of R’ Tanchum: A Chanuka light

that is placed twenty amos or higher from the  ground is invalid, just as in the cases of a succah and a mavoi.

Since the menorah will be outside one’s field of vision there won’t be פרסומי ניסא, (publicizing of the miracle) which is the whole goal of the mitzvah. (Rashi)

Rav Kahana said: Rav Nassan bar Manyumi expounded in the name of R’ Tanchum:
What is the meaning of the passuk in the parsha of the sale of Yosef, והבור רק אין בו מים – And the pit was empty; no water was in it? Do I not know that no water was in it since it already stated it was empty? Rather it is coming to teach us that there was no water in the pit, but snakes and scorpions were in it.

A question was asked in a Baraisa, what was the purpose of lighting the Menorah in the Beis HaMikdash, since Hashem, who was the source of the light during the forty years in the wilderness (meaning, the pillar of fire), surely does not need it? The Baraisa answers that the lighting of the Menorah was a testimony for all Mankind that the Shechinah dwells amongst Klal Yisrael.

Rav explains how the lighting of the Menorah was a testimony that the Shechina dwells amongst Klal Yisrael. The testimony  was from the ner ma’aravi (the western lamp). This was because the Kohen put the same amount of oil  in the western lamp that he put in all of the other lamps in the Menorah, yet the other lamps went out in the morning while the western lamp miraculously continued to burn into the next evening.