2- Shortening the prayer is the practice (sunnah) of the Prophet ﷺ and of his rightly guided successors during their travels.

3- The concession of shortening is universal: it covers journeys for pilgrimage, jihad, and every trip undertaken in obedience. Scholars have also attached to it all journeys that are merely permissible. Al-Nawawī said, “The majority hold that shortening is allowed in every lawful journey.” Some scholars barred it in a journey undertaken for sin, yet the sound position is that the concession is general and open to everyone.

4- This points to the Master’s kindness toward His servants and to the gracious ease of this Muḥammadan law, for He has lightened His worship for them. Since travel usually involves hardship He permitted a reduction in the prayer, and when the hardship is compounded by fighting an enemy He made the prayer even lighter.

5- In this ḥadīth “travel” is mentioned without restriction; it is not limited to long distances. It is therefore best to leave it unqualified, so that one may avail oneself of the concessions in anything people call a journey. To bind it to a fixed duration or a specified number of leagues lacks any sound proof.
Shaykh al-Islām Ibn Taymiyyah said: “The Lawgiver did not set a definition for travel, nor does the Arabic language prescribe a limit; one refers instead to common usage—whatever people regard as a journey is a journey.” End of quote.