The ruling on standing (for Supplication) in Muzdalifah and when does the Time for leaving it begin

Question :

What is the ruling on standing in Muzdalifah (for supplications) and spending the night there, and what is the amount of time for it? Also, when does the Hajj pilgrim begin leaving from it?

Answer:

Spending the night at Muzdalifah is Wajib (compulsory) according to the correct opinion. Some of the scholars have said that it is a pillar (of Hajj) and some have said that it is Mustahab (desirable). However, the correct view from the opinions of the people of knowledge is that it is Wajib (compulsory). Whoever leaves it off must slaughter an animal. The Sunnah is that the person does not leave from it until after the Fajr prayer and after the sky has begun to get bright before sunrise. He prays the Fajr prayer there and then when it begins to get light outside, he sets out to Mina while saying the Talbiyyah. The Sunnah is that he remembers Allâh after the prayer and he makes supplications. Then, when it becomes light outside, he sets out to Mina while saying the Talbiyyah.

It is permissible for the weak people among the women, men and elderly to depart from Muzdalifah during the last half of the night. The Prophet gave them this permission. In reference to those who are strong, the Sunnah for them is that they remain until they pray the Fajr prayer and until they remember Allâh much after the prayer. Then, they leave before the sun rises. It is also Sunnah to raise the hands while supplicating at Muzdalifah and facing the Qiblah, as is done at Arafat, and all of Muzdalifah is a place of standing.

Source:
Ash-Shaykh Ibn Baz
Fatawa Islamiyah, Vol. 4 Page 219