This resolved a previous poster's query as to whether a sick person who
must eat on Yom Kippur is required to recite the Kiddush.
There is a postscript to the story as well. Some time later, the Maskilim
('enlightened' ones) in Vilna put on a play portraying the events of that
Yom Kippur. The name of the play was "Sh'losha she'achlo" - "Three who
ate", alluding to the name of the seventh chapter of the Talmudic tractate
Berachos, but also referring to the three Rabbis who ate on that day to
alert everyone to the necessity of eating. It was a sly rebuff to Rabbinic
authority, in the manner of the Maskilim, as if to show that the Rabbis can
change the laws whenever they feel like it, including as well known and
important a law as to fast on Yom Kippur.
Of course, the flaw in the Maskilim's reasoning was two-fold:
#1) Obeying Rabbinic mandates and respecting their authority is as
important if not more important than fasting Yom Kippur [as evidenced by
"Lo sasur" - Do not deviate; another TF thread].
#2) In a case of medical danger there is actually a prohibition to fast,
and a mitzvah to eat.
Reb Yisroel, in publicly making Kiddush, was thus dramatizing the value of
human life. "Va'chai bahem" - "And you shall live by them" (Lev. 18:5) He
also secondarily taught the halachah of the requirement of that Kiddush.