It is sunnah for pilgrims to combine Maghrib and `Isha’ Prayers at the time of Maghrib with one Adhan and two Iqamahs upon arriving in Muzdalifah. No other supererogatory prayer is to be offered in-between. If they are performed separately there is nothing wrong but following the example of the Prophet (peace and blessings be upon him) is preferable.
In this regard, we will cite what Sheikh Sayyed Sabiq states in his well-known book, Fiqh As-Sunnah: “Upon arriving in Muzdalifah the Prophet (peace and blessings be upon him) offered Maghrib Prayer and two rak`ahs for `Isha’ Prayer. He ordered one single call (</>Adhan) for both `Isha’ and Maghrib Prayer, but a separate Iqamah for each. No other supererogatory Prayer is to be offered in-between these two Prayers. In the hadith recorded by Muslim we read that the Prophet (peace and blessings be upon him) arrived in Muzdalifah, and combined the Maghrib and `Isha’ Prayers, with one Adhan and two Iqamahs. He did not offer any other prayer in-between the two. Combining these prayers is, according to the consensus of the scholars, a sunnah, though there is disagreement as to those who offer these two prayers separately in their times. Most scholars consider it to be permissible, but maintain that following the example of the Prophet (peace and blessings be upon him) is far more preferable. Ath-Thawri and other knowledgeable people are of the opinion that a pilgrim offering Maghrib Prayer at any place other than Muzdalifah must repeat it. They are of the opinion, however, that offering Zhuhr and `Asr Prayers separately in their due times is permissible, but it is a disliked act.”