Bukhari

Hadith Commentary:
The meaning of the chapter is that one should also perform shortened prayers (qasr) in Mina.
This chapter, along with these ahadith, has already been discussed previously.
In the sixth year of his caliphate, Hazrat Uthman (radi Allahu anhu) performed the full prayer in Mina, but the other Companions considered this action of his as an act of caliphate, not as Sunnah.
Many reasons have been mentioned for Hazrat Uthman (radi Allahu anhu) performing the full prayer, one of which is that he considered both shortening the prayer (qasr) and performing the full prayer during travel to be permissible, so he acted upon the permissibility.
The reason for the naming of Mina and its full explanation has already been mentioned previously.

Hadith Commentary:
(1)
This chapter heading and all three ahadith mentioned within it have already appeared in the Book of Shortening the Prayer (Kitab Taqsir al-Salat). Imam al-Bukhari rahimahullah has narrated them here with a change of teacher.
(2)
In the sixth year of his caliphate, Uthman radi Allahu anhu began performing the full prayer (without shortening) in Mina. We have already mentioned the reasons for this previously, among which is that, in his view, both shortening (qasr) and performing the full prayer during travel were permissible acts. Therefore, he acted upon the permissibility due to some expediency. Although some of the noble Companions radi Allahu anhum disagreed with this action of his, foremost among them being Abdullah ibn Mas'ud radi Allahu anhu. In any case, pilgrims should perform the prayers of Dhuhr, Asr, and Isha in Mina in shortened form (qasr) during Hajj, while the Fajr and Maghrib prayers should be performed in full. However, the Sunnah prayers of Maghrib should not be performed.

1223. Commentary:
The "Sunan Rawatib" before or after the obligatory prayers, as "Sunan Mu’akkadah," are not established from the actions of the Messenger of Allah (sallallahu alayhi wa sallam) or the practice of the Rightly Guided Caliphs during travel, except for the Sunnahs of Fajr. Apart from this, if someone wishes to perform them as general voluntary prayers (nafl), it is not prohibited. As will be established from the ahadith in the following chapter, the Noble Prophet (sallallahu alayhi wa sallam) used to perform voluntary prayers (nawafil) even on his mount during travel. This issue is related to a person's own enthusiasm.