Spending the nights of the 11th, 12th (and optionally 13th) in Mina is obligatory; being present for the majority of each night fulfills the requirement, and missing it without excuse requires fidyah.
Yes, staying overnight in Mina during the Days of Tashreeq is considered wajib (obligatory) by the majority of scholars. Specifically, pilgrims should spend the nights of the 11th and 12th of Dhul Hijjah in Mina, with the 13th night being optional (as early departure on the 12th is permitted). The requirement is to be present in Mina for the majority of the night — roughly from Maghrib (sunset) to Fajr (dawn).
The tent cities of Mina are organized by country and Hajj group, with assigned camps. Life in the Mina tents is communal and simple — pilgrims sleep in air-conditioned tents, share meals, and use their time between stoning rituals for worship, Quran recitation, and rest. The days in Mina are spiritually significant as they are the Days of Tashreeq, during which the Prophet (peace be upon him) said: 'The Days of Tashreeq are days of eating, drinking, and remembrance of Allah.'
If a pilgrim does not stay overnight in Mina without a valid excuse, a fidyah (sacrifice of a sheep) is required according to the majority of scholars. Valid excuses include: genuine inability to find space in Mina (which does occur due to overcrowding), medical emergencies, or being assigned accommodation outside Mina boundaries by the authorities. Those whose camps are technically outside Mina's boundaries should still spend as much time as possible within the boundaries.
The Prophet (peace be upon him) said: 'The Days of Tashreeq are days of eating, drinking, and remembrance of Allah Most High.'
The Prophet (peace be upon him) said: 'The Days of Tashreeq are days of eating, drinking, and remembrance of Allah Most High.'
Source: Ibn Qudamah, Al-Mughni; al-Nawawi, Al-Majmu
The Prophet (peace be upon him) said: 'The Days of Tashreeq are days of eating, drinking, and remembrance of Allah Most High.'
Sahih Muslim #1141 (sahih)