Who knows eighty?
Please cite/link your sources, if possible. At some point in the next few days, I will:
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Eighty is the age described by Psalms for someone courageous (or strong, or disciplined; however you translate "gvurah.")
The Talmud considers the possibility that if someone is in their 70s we need to be more concerned that they'll die tomorrow than if they're in their 80s. While that seems counterintuitive, there was an AOJS article a while back looking at some longevity statistics that might support that. (Sorry, I don't recall the details; bonus points if anyone can find it please.)
Eighty are the answers of R' Yosef Engel, in a book called "Gvuros Shmonim" ("courage of eighty") based on the above Psalm, to the following question:
When dealing with Temple sacrifices: if the priest, while he's handling the sacrifice, has intent for it to be eaten at the wrong place or time, that inherently invalidates the sacrifice (known as pigul) immediately.
According to one Talmudic opinion, even the sacrifice's layman owner can invalidate it the same way.
Now the Torah describes a Temple procedure for the Sotah, a woman who allegedly committed adultery; and it involves a grain sacrifice. If the lay owner of a sacrifice can invalidate it too, why can't any woman in this situation void the procedure by having in mind "I want this sacrifice to be eaten ten years from now, in Alaska!"?
80 is the number of days that elapse after a woman who has given birth to a girl can resume her niddah cycle. (The first 14 days she is tamei regardless, and any bleeding during the next 66 days does not render her tamei.)
Moshe's age when he appears before Paroah
Yochanan Kohen Gadol served as Kohen Gadol for 80 years, but then became a Tzedoki. (Berachos 29a)
The city of Gufnis in Eretz Yisrael had 80 pairs of brothers who were Kohanim, married to 80 pairs of sisters who were Kohanos. (Berachos 44a)
That night, Pharoah's daughter (Bithiah) performed eighty different dances (Vayikra Rabbah 12:5; Encyclopedia of biblical personalities p. 124)
Eighty are the witches that Shimon Ben Shetach hanged.
(Mishnah Sanhedrin 6:4)