Bukhari

Hadith Commentary:
The correspondence between the chapter and the hadith is evident, and it is also clear that if someone does not fast during travel, then those who do fast are not permitted to reproach him verbally.
He is acting upon a legal concession (rukhsa) of the Shari‘ah, and no one has the right to prevent him from availing himself of this legal concession. This is an established principle for every legal concession in the Shari‘ah.

Hadith Commentary:
(1)
This hadith refutes those who hold the view that fasting during travel is futile and fruitless, and that there is no reward for it.

(2)
This hadith also shows that if someone does not fast while traveling, those who are fasting are not permitted to reproach him, because the one not fasting is acting upon a legal concession (rukhsa). No one has the right to prevent another from acting upon a legal concession. The statement of Allah, the Exalted, is:
﴿وَمَن كَانَ مَرِيضًا أَوْ عَلَىٰ سَفَرٍ فَعِدَّةٌ مِّنْ أَيَّامٍ أُخَرَ﴾ ()
“Whoever is ill or on a journey, then (he should fast) a number of other days.” ()
Imam al-Bukhari rahimahullah holds the view that if fasting during travel causes a person extreme hardship, then this is blameworthy for him; but for one who does not reach such a state, then whether he fasts or leaves it, there is no blame upon him. In Sahih Muslim, this is further clarified: Abu Sa‘id al-Khudri radi Allahu anhu said:
We would go out on campaigns with the Messenger of Allah sallallahu alayhi wa sallam, and during that time, no fasting person would reproach others, nor would one who broke his fast find fault with others. Whoever had the strength to fast would do so and that was good, and whoever felt weakness would leave it and that was good.
(Sahih Muslim, Kitab al-Siyam, Hadith: 2618(1116))

(3)
Hafiz Ibn Hajar rahimahullah says:
This hadith is decisive in ending the disagreement in this matter.
(Fath al-Bari: 4/237)

Hadith Authentication (Takhrij al-Hadith):
[وأخرجه البخاري 1947، من حديث مالك به ورواه مسلم 99/118، من حديث حميد الطّويل به وصرّح بالسماع عنده]

Jurisprudential Explanation (Tafaqquh):
➊ During travel, both fasting and breaking the fast are permissible.
● If one breaks the fasts of Ramadan during travel, then later one must make up those fasts (qada).
● If the heat is intense during travel and there is severe hardship, then breaking the fast is preferable.
➋ Also see: [ح 465]
➌ Sayyiduna Abdullah ibn Umar radi Allahu anhu would not fast during travel. [موطأ امام مالك 1/295 ح663 وسنده صحيح] Whereas, Urwah ibn al-Zubayr rahimahullah would fast during travel. [ايضاً ح664 وسنده صحيح]
➍ If both actions are established in the Shariah, then one should not object to the other.
➎ It is absolutely correct to refute anything that is against the Book and the Sunnah.