Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.115B.
Section : Combining the salah at ‘Arafa and al-Muzdalifah.
The scholars are in agreement that one is to combine the zuhr and ‘asr prayer during the time of the zuhr prayer, at ‘Arafa [during the performance of the pilgrimage], and the maghrib and ‘isha prayers during the time of the ‘isha at muzdalifah, following the example of the Prophet.