شَهۡرُ رَمَضَانَ الَّذِىۡٓ اُنۡزِلَ فِيۡهِ الۡقُرۡاٰنُ هُدًى لِّلنَّاسِ وَ بَيِّنٰتٍ مِّنَ الۡهُدٰى وَالۡفُرۡقَانِۚ فَمَنۡ شَهِدَ مِنۡكُمُ الشَّهۡرَ فَلۡيَـصُمۡهُ ؕ وَمَنۡ کَانَ مَرِيۡضًا اَوۡ عَلٰى سَفَرٍ فَعِدَّةٌ مِّنۡ اَيَّامٍ اُخَرَؕ يُرِيۡدُ اللّٰهُ بِکُمُ الۡيُسۡرَ وَلَا يُرِيۡدُ بِکُمُ الۡعُسۡرَ وَلِتُکۡمِلُوا الۡعِدَّةَ وَلِتُکَبِّرُوا اللّٰهَ عَلٰى مَا هَدٰٮكُمۡ وَلَعَلَّکُمۡ تَشۡكُرُوۡنَ
It has been left to the option of the individual to observe or not to observe fasts during a journey. Some of the Companions of the Holy Prophet observed fasts and some did not when they were on a journey with him and neither raised any objection against the other. The Holy Prophet himself sometimes observed fasts on a journey and sometimes did not. Once he saw people gathered round a man who had fallen to the ground and asked what was the matter with him. He was told that he had become too weak to stand on account of observing fasts; he remarked that it was no virtue to observe fasts in such a condition.
During war time, he used to issue orders for postponing the fasts. Hadrat 'Umar has related that they did not observe fasts twice during the month of Ramadan when they went to war under the command of the Holy Prophet: on the occasion of the battle of Badr and at the conquest of Makkah. Ibn 'Umar says that on the eve of the conquest of Makkah, the Holy Prophet declared, "As we are going to fight our enemy you should postpone your fasts so that you may conserve your strength to tight." 'There is no clear injunction from the Holy Prophet for the prescription of a minimum standard of distance for postponing the fasts. His Companions also differed in practice with regard to the standard. But it is obvious that the fast may be postponed for that distance which is commonly understood to be a journey and in which one begins to feel like one is on a journey.
There is a difference of opinion as to whether the people of a city, which is attacked by an enemy, can postpone the fast for the sake of Jihad, in spite of being the residents. Some scholars do not allow this. But Imam Ibn Taimiyyah has maintained with strong arguments that postponement of the fast under such circumstances is permissible.
Allah is so bountiful that He does not want to deprive His servants of the blessings of fasting. Therefore, He has not confined it to the month of Ramadan but has opened another way for its completion for those who fail to complete it during this month for genuine reasons. They should make up the deficiency by observing fast on other days in order to show their gratitude for the revelation of the Qur'an during the month of Ramadan.
It is clear from this verse that fasting in Ramadan has been prescribed not only as a form of worship and a training for piety, but also to show gratitude for the great blessing of the Revelation of the Qur'an during the month of Ramadan. And the best way to show gratitude for a favour is to fulfil the object for which it was bestowed and to prepare oneself for its completion as best as one can. The object for which Allah has bestowed the Qur'an upon us is to reveal His Will so that we may fulfil it ourselves and persuade others to do the same. Fasting provides the best training for the fulfilment of this object and is both a devotion and a sign of gratitude for the favour shown in the form of the Qur'an.
Tafsir Qur'an Wiki:
This verse establishes fasting in Ramadan as obligatory for all healthy non- travelling Muslims, with no concessions except for the elderly, as pointed out above: “Whoever of you is present in that month shall fast throughout the month.” It has thus become binding on all Muslims who either see the new moon of the lunar month of Ramadan themselves or learn of it by any other reliable means, to observe the fast in Ramadan. But as this is a general order applicable to all, a reiteration of the concession given in special cases immediately follows: “But he who is ill or on a journey shall fast instead the same number of days later on.”
The sūrah gives the Muslims yet another incentive to keep the fast: “God desires that you have ease. He does not desire that you be afflicted with hardship.” This statement encapsulates the fundamental principle on which all Islamic religious duties are founded. They are intended to be easy, not arduous. This indicates a generous and realistic outlook on life as a whole. It instils in the Muslim heart a tolerant, easy and agreeable attitude. Religious and social activities and responsibilities are discharged with ease, confidence and assurance, in the happy knowledge that God’s purpose is to enable man to go through life with the minimum of hardship or discomfort.
To complete a whole month, sick people or those who travel in Ramadan and avail themselves of the special concession are required to make up for days missed by fasting an equal number of days at a later date in the year: “You are, however, required to complete the necessary number of days.”
Fasting is an occasion to celebrate God’s guidance, glory and grace. Hence the requirement “to extol and glorify God for having guided you aright and to tender your thanks.” It is a time during which believers can feel and appreciate God’s favours and reciprocate with thanks, submission and gratitude. In so doing, Muslims cultivate the precious and vital quality of taqwā, or God-fearing; a main objective of fasting.
Thus, we can see how evident God’s grace is in the imposition of the duty of fasting which, on the face of it, seems hard and demanding. We can clearly see its educational and disciplinary benefits for a nation being prepared for the leadership of mankind, guided by a genuine fear of God, a keen sense of accountability, and a vigorous conscience.