It is well known that, if we were to take the wording at face value, we would say that departure before the middle of the night is permissible, since it is still a departure at night. But this is not the view held by the author, may Allah have mercy on him.
Moreover, if we say that the obligation is to remain overnight for most of the night, then the middle of the night does not constitute most of it. For the people departed from ‘Arafah after sunset, and the journey from ‘Arafah to Muzdalifah takes an hour and a half or two hours. Thus, part of the sound understanding of Asma’ bint Abu Bakr, may Allah be pleased with her, was that she would wait until the moon had set, and then depart. (1) On the night of the tenth, the moon sets after approximately two-thirds of the night has passed—perhaps slightly more or slightly less. It is as though she, may Allah be pleased with her, regarded this as the midpoint of the night, but calculated the half from the time people arrived at Muzdalifah. If we calculate the midpoint from their arrival at Muzdalifah, it exceeds the actual midpoint—from sunset until dawn—by approximately the amount represented in Asma’s calculation, namely the setting of the moon. This is the correct view: what counts is the setting of the moon. Or, if you prefer, one may say that what counts is remaining in Muzdalifah for most of the night, while excluding from the night the time taken to travel from ‘Arafah until reaching Muzdalifah. Thus, the view adopted by Asma’, may Allah be pleased with her, corresponds to spending most of the night there.
His statement, “and before it, a sacrifice is due”: it says in al-Rawd, “This applies whether he knows the ruling or is ignorant of it, and whether he acts deliberately or forgetfully.”