Take the 2-minute tour ×  The first Mishnah in Berachoth quotes
R' Eli'ezer's opinion that the time for reciting Shema' in the
evening extends only until the end of the first shift (the
Kohanim would serve in the Beith HaMikdash in three shifts
throughout the night). If a particular set of Kohanim are on
duty in the first shift, does that mean that, according to him,
they can't say Shema' (or perhaps are exempt)?  share|improve
this question Because they're "Osek b'mitzvah patur min
hamitzvah"? Also, I thought it was referring to shifts in
Shamayim (daf 3a), not in the Beith HaMikdash. –  zaq Aug 3 '12
at 18:26 @zaq, I had that thought. But the Gemara doesn't raise
the question. Tosafoth ask the same question on a different
Beraitha, but not on this Mishnah. As to your second point,
we're not there yet! –  Seth J Aug 3 '12 at 18:30 Spoiler Alert!
I'm not sure, but I don't think they'd be Patur. They might be
considered workers who are entitled/required to take a break to
say Shema and Birkat Hamazon, since th