Upon arriving at مزدلفة, combine and shorten Maghrib (3 ركعةs) and Isha (2 ركعةs) الصلوات with one adhan and two iqamahs. Then rest until Fajr. النبي said: 'I have stopped here, but all of مزدلفة is a stopping place.' Collect pebbles for the stoning of الجمرات and spend the night in remembrance of Allah.
اللَّهُمَّ إِنِّي أَسْأَلُكَ أَنْ تَرْزُقَنِي فِي هَٰذَا الْمَكَانِ جَوَامِعَ الْخَيْرِ كُلِّهِ، وَأَنْ تُعَافِيَنِي مِنْ جَوَامِعِ الشَّرِّ كُلِّهِ
Allahumma inni as'aluka an tarzuqani fi hadhal-makani jawami'al-khayri kullih, wa an tu'afiyanì min jawami'ash-sharri kullih.
Meaning: O Allah, I ask You to grant me in this place all comprehensive good, and to protect me from all comprehensive evil.
Source: Sahih Muslim #1218مزدلفة (also called al-Mash'ar al-Haram — the Sacred Monument) is mentioned in القرآن: 'When you depart from عرفة, remember Allah at al-Mash'ar al-Haram' (2:198). Spending the night here under the open sky is a واجب (واجب) act of الحج. The simplicity of sleeping on the ground creates a profound sense of equality and humility before Allah.
اللَّهُمَّ إِنِّي أَسْأَلُكَ أَنْ تَرْزُقَنِي فِي هَٰذَا الْمَكَانِ جَوَامِعَ الْخَيْرِ كُلِّهِ، وَأَنْ تُعَافِيَنِي مِنْ جَوَامِعِ الشَّرِّ كُلِّهِ
The Prophet (peace be upon him) came to Muzdalifah and prayed Maghrib and Isha there with one adhan and two iqamahs. He did not pray any voluntary prayers between them. Then he lay down until dawn.