cellio | daf bit: Pesachim 7

Tractate Pesachim covers the laws of Pesach, beginning with the search for chametz on the night before. The search for chametz commences with a b'racha. R. Papa said in Raba's name that the text is "blessed art Thou... who has commanded us concerning the removal of leaven". But maybe instead of "concerning..." it should be "to remove leaven"? Various b'rachot are brought as examples. For circumcision or slaughter we say "concerning" except if the father (circumcision) or owner (slaughter) is the one who is doing it, in which case he says "to...", because the obligation is actually on the father/owner, not the agent who (otherwise) performs the mitzvah on his behalf.

But wait -- for taking up the lulav we say "concerning"? This is different because in the very moment that he lifts it up (while beginning the b'racha) he fulfills the obligation, so technically he has already completed the mitzvah before he finishes speaking and so can't speak about it as if it's in the future.

But wait! When he enters the sukkah he says "to dwell in the sukkah", not "concerning", but he's already in it? How is that any different than the lulav? The answer, the g'mara says, is that dwelling in the sukkah is a commandment throughout the entire seven days of the festival, so there is future fulfillment too. (7b)

So the rule is...unclear. (And why doesn't the sukkah reason apply for lulav, which we also do every (week)day during Sukkot? Perhaps lulav is instantaneous (you've lifted it up and then you're done) while dwelling is ongoing?)

I actually asked about the two b'racha formations on Mi Yodeya a couple years ago; later interpreters disagree on why we sometimes say one form or the other, too.