He (the Holy Prophet) observed the two prayers (together) with one iqama.
Sahih Muslim Book 15, Hadith 317
← Previous Hadith Sa'id b. Jubair reported that he observed the sunset and 'Isha' prayers at Muzdalifa with (one) iqama. He narrated on the authority of Ibn 'Umar (Allah be pleased with them) that he observed prayers like this and Ibn 'Umar (Allah be pleased with them) narrated that Allah's Apostle (ﷺ) did like this.

Sahih Muslim Book 15, Hadith 316 Next Hadith → Ibn 'Umar rep rte that Allah's Messenger (ﷺ) combined the sunset and 'Isha ' prayers at Muzdalifa. He observed three rak'ahs of the sunset prayer and two rak'ahs of the 'Isha' prayer with one Iqama.

Sahih Muslim Book 15, Hadith 318