Rav Natan bar Mur Ukva said in the name of Rebbi Yehuda that until "Al levavecha" one must stand. Rashi explains because that is where you have to have Kavana. Then gemara says that Rabbi Yohanan said that this applies to the whole first parasha...and that "Va'azda rabbi yohanan le'tamai" because he says that halacha is like rab Aha who said in the name of Rebbi Yehuda.
My first question is that if rabbi yohanan agrees with rab aha who spoke in the name of rebbi yehuda, then what's the argument over here between rebbi yehuda and rebbi yohanan? More importantly, my second question is that if you go back to the top of the amud, didn't rebbi yehuda say that kavana is needed for the entire first perek (and therefore that SHOULD be for how long one must stand for)? How come here he says that "standing" is only until "al le'vavecha", if you really need to have kavana until the end of the first perek?
Thank you for your time.
Yair Chaya, Brooklyn, NY
if you bear in mind that Rebbi Yochanan is quoting Rebbi Acha in the name of Rebbi Yehudah the Tana, whereas R. Nasan bar Ukva is quoting Rav Yehudah, the Amora, all your questions will be answered.
Incidentally, the latter is not talking about standing (which is not required for Keri'as Shema), but about standing still (as opposed to walking; see Tosfos DH 'Al Levavecha).
Wishing you a Kesivah va'Chasimah Tovah
Eliezer Chrysler