Imagine the following case. You wake up in the middle of the night, pick up a lulav (with its accompanying three species), and hold them in your hands until a few minutes after daybreak. Now one cannot fulfil one’s obligation of shaking a lulav at night, so in our scenario has our intrepid insomniac fulfilled his mitzvah of shaking lulav given that he was holding the lulav during the day? This is an old question which has been debated back and forth between the poskim. The Chazon Ish held that he has fulfilled his mitzvah, whilst the Chassam Sofer held that one had done the mitzvah.
Their machlokes is based on what the Torah means when it said you shall take (u’lekachtem lachem) in reference to the four species. The Chassam Sofer held that it means that you must pick them up, in which case since our night-watchman picked up the lulav at night, he has not performed the mitzvah.
But the Chazon Ish held that you shall take merely means to have the four species in your hands (as opposed to an active action of taking), and thus, since the four species were in our sleepy hero’s hands after daybreak then he has fulfilled his mitzvah.
Personally I wouldn’t wake up in the middle of the night and stand there for a few hours with my lulav, just to be on the safe side!
