Reference: Fataawa al-Hajj wal-‘Umrah waz-Ziyaarah – Page 98
Question: What is the ruling about [starting] the stay in Muzdalifah before the first half [of the night]?
Response: It is obligatory upon the one performing the Hajj to spend the tenth (10th) of Dhul-Hijjah until [the time of] Fajr, except for the one who has an excuse such as illness or the like. So it is permissible for him or whoever has undertaken responsibility for him to depart to Minaa after half the night has passed in accordance with the Prophet ﷺ having the spent the night there until [the time of] Fajr and him having granted those with a [legal] excuse to depart from Muzdalifah to Minaa after half the night [had passed].
