Bukhari

Hadith Commentary:

‘Ayni has transmitted six opinions of the scholars regarding this matter. The last opinion is that the call to prayer (adhan) should be given for the first prayer, and for both prayers, separate iqamah (takbir) should be pronounced. This is the view of the Shafi‘iyyah and Hanabilah, and this is the preferred opinion.’

Hadith Commentary:
(1)
From these ahadith it is understood that when Maghrib and Isha are performed together at Muzdalifah, no supererogatory (nafl) prayers or the like should be performed between them, nor should any nafl prayers be performed after them, because the purpose of combining (jam‘) is that no other prayer should be performed between them.
To interpret this as meaning that it is only prohibited to perform nafl prayers immediately after Isha, but that they may be performed at any other part of the night, is mere wordplay, because in the hadith narrated from Jabir radi Allahu anhu, it is explicitly stated that the Messenger of Allah sallallahu alayhi wa sallam, after performing the Isha prayer, lay down until Fajr appeared.
(Sahih Muslim, Al-Hajj, Hadith: 2950(1218))

(2)
The Sunnah is that on this night, after performing two rak‘ahs of Isha prayer, a person should go to sleep.
There is goodness and blessing in following the Sunnah, and on the Day of Judgment, this will be the means of salvation.
In these places, it is beloved to the Lawgiver alayhis salam that Maghrib and Isha be performed together.
No supererogatory prayers should be performed between them or after Isha.
Whatever deed pleases the Beloved, the claimant of love should also perform that deed with zeal and eagerness. However, Abdullah ibn Mas‘ud radi Allahu anhu used to perform two Sunnah prayers after Maghrib at Muzdalifah.
(Sahih al-Bukhari, Al-Hajj, Hadith: 1675)
It is possible that he did not perform them together with the Isha prayer.
And Allah knows best.

482. Commentary: The Maghrib prayer remains three rak‘ahs both during travel and at home because it is the witr (odd-numbered prayer) of the day; it is not possible to halve it. If only two rak‘ahs are performed, it will no longer remain witr, whereas the ‘Isha prayer becomes two rak‘ahs during travel.

592. Commentary: The apparent wording indicates that the Prophet (sallallahu alayhi wa sallam) performed delayed combination (jam‘ ta’khir), meaning that after the time of Maghrib had ended and the time of ‘Isha had begun, both prayers were performed. Thus, it is permissible to combine prayers with delay (jam‘ ta’khir) during travel, as there is ease in this. And Allah knows best.

601. Commentary: That is, in the state of travel, a person can combine two prayers, and this is a matter of consensus.

Hadith Commentary: Benefits and Issues: According to Imam Shafi‘i rahimahullah, Imam Ahmad rahimahullah, and Ibn Hazm, it is Sunnah in Muzdalifah to perform both prayers with one call to prayer (adhan) and two calls to commence (iqamahs). The same position is held by Imam Zufar and Imam Tahawi rahimahullah. According to some of the Hanafis, there should be one adhan and one iqamah for both prayers. According to one narration from Imam Ahmad rahimahullah, as well as the opinion of Imam Khiraqi and Ibn al-Mundhir, there should be a separate call to commence (iqamah) for each prayer without an adhan. According to Imam Malik rahimahullah, there should be a separate adhan and a separate iqamah for each prayer. This was the practice of Ibn ‘Umar, ‘Umar, and Ibn Mas‘ud radi Allahu anhum; however, there is no marfu‘ (attributed directly to the Prophet sallallahu alayhi wa sallam) narration regarding this matter.

1:
In contrast, there is a narration of Jabir radi Allahu anhu in Sahih Muslim that the Prophet sallallahu alayhi wa sallam performed both prayers with one adhan and two iqamahs, and this is the preferred view,
and Allah knows best.

Note:
(This hadith is authentic with the mention of a separate iqamah for each prayer/see the next narration)

1931. Commentary: In this too, there is a mention of one iqamah, which is not correct, as has been discussed in the previous hadith.

1929. Commentary: In this hadith, the mention is made of performing two prayers with a single takbir. However, it is established from more authentic ahadith that for each prayer, a separate iqamah should be pronounced. (Sahih al-Bukhari, Hajj, Hadith 1673) Regarding this very hadith, Shaykh al-Albani says that this narration—with the addition of (li kulli salat) (i.e., a separate takbir was pronounced for each prayer)—is authentic.

1933. Commentary: Allamah al-Albani rahimahullah writes regarding this narration that the words (faqala as-salah) (he turned towards us and said: Prayer!) are shaadh (anomalous). However, the words (faqama as-salah) (he had the call to prayer made) are more authentic.

1932. Commentary: In this hadith as well, only one takbir is mentioned, which is not correct. See the benefits of the previous ahadith.

661. Commentary: In this narration, the mention is of a separate iqamah for each prayer, whereas in the previous three narrations, there is mention of a single iqamah for both prayers, and all four narrations are from Ibn Umar (radi Allahu anhuma). The first narration of the previous chapter is from Jabir (radi Allahu anhu), and in it, there is explicit mention of two iqamahs, and this is what is correct. Explicit mention of two iqamahs has also come from Usamah (radi Allahu anhu). Therefore, in the narration where a single iqamah is mentioned, it will mean one iqamah for each prayer, or else the narration with a single iqamah is shaadh (anomalous). However, some say that when such reconciliation is possible, then there is no need to claim shudhudh (anomaly). However, a single adhan is sufficient, because it is only for calling the people. In the case of combining (jam‘) the prayers, the people are already present for the second prayer.

(1) “With one iqamah (call to commence prayer)” — The Hanafis have adopted this view, provided that the ‘Isha prayer is performed immediately after Maghrib, and if there is an interval, then a separate iqamah should be given for ‘Isha. However, in ‘Arafat, Dhuhr and ‘Asr will be performed with two separate iqamahs because ‘Asr is being performed before its (prescribed) time. But the position of the Hanafis is not correct, because this very narration is also found in Sahih al-Bukhari (Hadith no. 1673), where it is explicitly stated that there was a separate iqamah for each of the two prayers, and the great hadith scholar Shaykh al-Albani rahimahullah has declared these very words to be “preserved.” Therefore, the preferred and correct position is that in the case of combining two prayers, a separate iqamah should be given for each prayer. This is also the view of the majority of the scholars. However, there will be only one adhan (call to prayer).

(2) “No supererogatory (nafl) prayers were performed” — In the case of combining two prayers, no supererogatory (nafl) prayers are to be performed, whether they are combined during Hajj, or during a general journey, or (out of necessity) at home. This is an agreed-upon principle. Neither in between, nor at the end, that is, neither after the first prayer nor after the second. Whether it is a case of combining at the earlier time (jam‘ taqdim), as was done in ‘Arafat, or combining at the later time (jam‘ ta’khir), as was done in Muzdalifah.

The narration of Ibn Umar radi Allahu anhu is found in Sahih al-Bukhari with the wording "a separate iqamah for each prayer." See: (Sahih al-Bukhari, al-Hajj, Hadith: 1673), and this is what is preserved.