Bukhari

Hadith Commentary:
In all the aforementioned ahadith, there is mention of the Farewell Pilgrimage (Hajjat al-Wada‘) in one way or another.
For this reason, the Imam rahimahullah has cited these ahadith here, which is evidence of his consummate ijtihad (independent juristic reasoning).
In fact, from each and every hadith, the establishment of many rulings is derived.
That is why most of these ahadith have been mentioned under several chapters, as will be evident to those who study carefully.

Hadith Commentary:
On the ninth day of Dhul-Hijjah, in the plain of Arafat, the Zuhr and Asr prayers are performed together in advance (jam‘ taqdim), meaning that Asr is performed at the time of Zuhr. In Muzdalifah, Maghrib and Isha are performed together in delay (jam‘ ta’khir), meaning that Maghrib is performed at the time of Isha.
This is done not due to travel, but because of the rites of Hajj.
It should be noted that in all these hadiths, in one way or another, there is mention of the Farewell Pilgrimage (Hajjat al-Wada‘), which is why Imam Bukhari rahimahullah has mentioned these hadiths here.
In fact, the respected Imam has derived multiple legal rulings from these hadiths, which is a clear and manifest proof of the Imam’s status as a mujtahid.

Hadith Commentary:
Muzdalifah is called "Jam‘" because Adam and Hawwa (alayhimas-salam) were united there.
Some have said that it is called so because two prayers are combined there. Ibn al-Mundhir has transmitted consensus (ijma‘) on the point that in Muzdalifah, no supererogatory (nafl) or sunnah prayers should be performed between the two obligatory prayers.
Ibn al-Mundhir said: Whoever performs sunnah or nafl prayers in between, his combining (jam‘) will not be valid.
(Wahidi)
Hujjat al-Hind, Hazrat Shah Waliullah Muhaddith Dehlawi rahimahullah, states:
“And indeed, the combining between Zuhr and ‘Asr, and between Maghrib and ‘Isha’, is because on that day the people have a gathering the like of which is not found in any other place, and the single congregation (jama‘ah) is what is sought, and it is necessary to establish it in such a gathering so that all those present may witness it, and it is not feasible for them to gather at two separate times. Also, because the people are occupied with remembrance (dhikr) and supplication (du‘a), which are the duties (wazifah) of this day, while observance of the prayer times is the duty throughout the year. In such a case, preference is given to this unique and rare matter. Then he mounted and came to the place of standing (mawqif), faced the qiblah, and remained standing until the sun set and the yellowishness had diminished a little, then he departed.” (Hujjat Allah al-Balighah)
On the Day of ‘Arafat, Zuhr and ‘Asr were combined and performed together, and in Muzdalifah, Maghrib and ‘Isha’ were combined, because on that day in these sacred places, there is such a gathering of people as is not found anywhere else, and the Lawgiver (sallallahu alayhi wa sallam) desires a single congregation, and in such a gathering it is necessary to establish a single congregation so that all may witness it, and it would be difficult for all to gather at two separate times. Moreover, on that day, people are engaged in remembrance and supplication, which are the duties of that day, while observance of the prayer times is the duty throughout the year, and in such a situation, preference is given to something unique and rare.
Then he (sallallahu alayhi wa sallam) departed from there (from Namirah after completing Zuhr and ‘Asr), came to the standing place in ‘Arafat, and remained standing there until the sun set and the yellowishness had diminished, then departed from there to Muzdalifah.
In summary, combining these prayers at these places is especially beloved to the Lawgiver (alayhi as-salatu wa as-salam).
Therefore, whatever pleases the Beloved should also be performed eagerly and enthusiastically by those who claim to love him.

This issue is also agreed upon: the Maghrib prayer will not be performed at ‘Arafat or on the way, but rather it will be performed at Muzdalifah, even if the night reaches its halfway point. However, the return from ‘Arafat will take place after sunset.

606. Commentary: The time for Maghrib occurs while at Arafat, but the command of the Shari'ah is that the Maghrib prayer should be performed at Muzdalifah, not at Arafat. And by the time one reaches Muzdalifah, it is inevitably the time for Isha. Therefore, both these prayers are performed together at the time of Isha. This ruling is agreed upon by consensus.

Benefit:
It is established from the hadith that Maghrib and Isha should be performed together at Muzdalifah.