What do Erev Shavuos & Hoshana Rabah have in common ?
There is something forbidden to be done on only two days (weekday) in the year..
The two days are, Erev Shavuos & Hoshana Rabbah.
" The minhag is not to do Hakazas Hadam (bloodletting)
on every Erev Yom Tov " (Shulchan Aruch O.Ch 468 – 10 ).*
There is a type of bloodletting with a cup where no blood is removed
from the body. All it does is brings up the blood to the surface of the
skin. (in Yiddish it’s called “Bankess)
The Mishna Verura sk 38 writes that "Bankess" (kep zetsin) is allowed
on Erev Yom Tov , except for, on Hoshana Rabbah (Yom Hadin) and on
Erev Shavuos. (SheidTabuach comes out)
Shu"t Mahri Brona (118) writes that the Mahri Weil went to the bathhouse in Erfurt
(Germany) on Erev Shabbos - Erev Shavuos (Sunday Monday -Shavuos) and told
the Bachurim not to do Hakazas Dam (blood letting) because it is considered as
Erev Yom Tov.
They didn't listen to him, and became dangerously sick . The Mahri Weil said they
deserved this to happen to them, for not listening to the Psak from his Rebbe the
Mahril "On a Friday that is a day before Erev Yom Tov, it is also Assur to do Hakazas Dam".
*The Gemoro in Shabbos 129b says on Erev Shavuos a Sheid called Tabuach came
out and said “ If the yidden won’t bemekabel the Torah I will slaughter their
flesh and blood. Chazal were gozer not to do Hakazas Hadam every Erev Yom Tov
because of Erev Shavuos.