Abu Dawud

Benefits and Issues:
➊ For the person who cannot bear the hardship of fasting while traveling and experiences distress from fasting, it is obligatory (wajib) and preferable for him to break his fast.
➋ Otherwise, it is also established from the Prophet sallallahu alayhi wa sallam and the noble Companions radi Allahu anhum that they kept the fast while traveling.

Hadith Commentary:
From this hadith, those people have derived evidence who consider breaking the fast (iftar) necessary during travel.
The opponents say that what is meant by this is only when fasting during travel causes hardship; in such a situation, breaking the fast is, by consensus, superior.

Hadith Commentary:
(1)
The Ahl al-Zahir have taken evidence from this hadith that it is not permissible to fast while traveling. If someone does fast, that fast will not be valid. However, this hadith pertains to a specific individual upon whom shade was provided and who had reached the brink of destruction. On this basis, the Messenger of Allah (sallallahu alayhi wa sallam) said:
“There is no virtue in fasting in such a state that the fasting person’s life is endangered, especially when Allah, the Exalted, has granted a concession to break the fast in such circumstances. For such a person, it is better to leave the fast.”
In one narration, the Messenger of Allah (sallallahu alayhi wa sallam) said:
“The one who fasts during travel in Ramadan is like the one who breaks the fast while residing (not traveling).”
(Sunan Ibn Majah, Kitab al-Siyam, Hadith: 1666)
This narration is munkar (denounced) and weak.
(Silsilat al-Ahadith al-Da‘ifah, Hadith: 498)
(2)
In a narration of Sahih Muslim, it is mentioned that the Messenger of Allah (sallallahu alayhi wa sallam) set out from Madinah Tayyibah for the conquest of Makkah during Ramadan. He was in a state of fasting. When he reached the place of Kura‘ al-Ghamim, it was said to him that fasting had become very difficult for the people and they were looking towards you. The Messenger of Allah (sallallahu alayhi wa sallam) called for a cup of water after ‘Asr and drank it in front of the people. After that, it was reported to him that some people had not broken their fast. He said:
“These are the disobedient ones, these are the disobedient ones.”
(Sahih Muslim, Kitab al-Siyam, Hadith: 2610(1114))
The meaning of this hadith is also that when fasting becomes a cause of hardship, it should be left during travel.

Such a fast “of this kind” by which other people also remain in difficulty—someone removes clothing, someone sprinkles water, and so on.