Yedidya Israel asked:
Why the verse Vayalen Sham Ki Ba HaShemesh isn't a proof that Biat HaShemesh is sunset?
Yedidya Israel
The Kollel replies:
A good Kashya!
The Kashya is of course confined to Rashi's interpretation of Bi'as Oro. According to Tosfos, the Gemara's dilemma is whether "Ba ha'Shemesh" refers to Sheki'as ha'Chamah or to Tzeis ha'Kochavim, in which case you would not really have a proof from "Vayalen Sham ki Va ha'Shemesh.
Perhaps according to Rashi, we could have brought a proof from there, but it was not necessary, as we have a proof from the Pasuk under discussion itself that it means Tzeis-ha'Kochavim (and according to the Yerushalmi, the proof is from the Beraisa in connection with the Sugya under discussion).
Kol Tuv,
Eliezer Chrysler