Staying in Muzdalifah Before The First Half of The Night
What is the ruling about starting the stay in Muzdalifah before the first half of the night?
It is obligatory upon the one performing the Hajj to spend the 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 Mina after half the night has passed in accordance with the Prophet (Peace and blessings be upon him) 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 Mina after half the night had passed.
Sheikh Ibn Baz