Bukhari

Hadith Commentary:
Allamah Hafiz Ibn Hajar rahimahullah states:
It has been said that the intended meaning is that the prayer (salat) does not become waived even when one is unable to dismount from the riding animal, nor can it be delayed beyond its appointed time; rather, it must be performed in whatever manner one is able, as indicated by the verse.
(Fath al-Bari)
That is, the purpose is that even when the worshipper is unable to dismount from the mount, the prayer is not waived, nor can it be postponed from its time; rather, in every situation, one must perform it according to one’s ability, as the above verse indicates.
In the present era, there are many such situations in trains, cars, and airplanes where it becomes impossible to disembark. In any case, the prayer should be performed at its appointed time in whatever way is possible.
In view of such difficulties, the Lawgiver (sallallahu alayhi wa sallam) has permitted the combining of two prayers at one time, and during travel, shortening (qasr) is allowed, and in times of jihad, even further concessions have been given, but the prayer itself has not been excused.

Hadith Commentary:
(1)
At another place, Hazrat Nafi‘ clarifies that when Hazrat Ibn ‘Umar radi Allahu anhu was asked about the prayer of fear (salat al-khawf), he would inform about its method, and would also say that if the situation became more severe, people would perform the prayer standing on foot, and if mounted, they would perform it on their mounts, whether or not they were able to face the qiblah at that time. Hazrat Nafi‘ said, “I am confident that Hazrat Ibn ‘Umar radi Allahu anhu must have stated this after learning it from the Messenger of Allah sallallahu alayhi wa sallam.” (Sahih al-Bukhari, al-Tafsir, Hadith: 4535)

(2)
Imam Bukhari rahimahullah has, at this point, narrated this report on the authority of Mujahid, but has not mentioned Mujahid’s statement anywhere, due to which there has arisen a difference in the understanding of the present wording. However, ‘Allamah Isma‘ili has transmitted Mujahid’s statement that when there is an encounter (confrontation) with the enemy, prayer can be performed even by signaling with the head. Similarly, the statement of Hazrat Ibn ‘Umar radi Allahu anhu has also been narrated in the same manner as Mujahid’s, that when there is an encounter with the enemy, remembrance (dhikr) is done with the tongue and prayer is performed by signaling with the head, as is transmitted from Ibn ‘Umar radi Allahu anhu. However, the difference between the two statements is that Mujahid adopted this position based on his own opinion, whereas Hazrat Ibn ‘Umar radi Allahu anhu’s position is based on a hadith narrated from the Messenger of Allah sallallahu alayhi wa sallam. The explanation of the narration given by Imam Bukhari rahimahullah has been correctly provided by Imam Ibn Battal, as we have mentioned. (‘Umdat al-Qari: 140/5)

(3)
Hafiz Ibn Hajar rahimahullah has considered the word “qiyaman” in “idha ikhtalatu qiyaman” to be a scribal error (tashif). He states that in reality, this word is “innama,” because in the narrations it is (idha ikhtalatu fa-innama huwa al-isharatu bi’l-ra’s). (Fath al-Bari: 2/556) However, in our view, there is no need to consider it a scribal error, because Imam Bukhari rahimahullah has taken the meaning of “rijalan” as “qiyaman.” This meaning can only be correct if the word “qiyaman” in the narration is accepted as authentic; otherwise, Imam Bukhari rahimahullah’s heading would remain without evidence. And Allah knows best.