What is the basis for shortening the prayer (Qasr) during travel?

Primary text

Shortening the prayer (Qasr) is established by the Book (Quran), the Sunnah, and scholarly consensus (Ijma). The basis in the Quran is the verse: {And when you go forth [to travel] in the land, there is no blame upon you if you shorten the prayer, if you fear that those who disbelieve may put you into trial} (Quran 4:101). This fear condition was lifted by a tradition where the Prophet (peace be upon him) clarified that this shortening is a charity accepted by the Muslim, as reported by Muslim from Ya'la ibn Umayyah questioning Umar ibn Al-Khattab. The Sunnah confirms this practice, as the Prophet (peace be upon him) consistently shortened prayers during all his travels, including Hajj, Umrah, and warfare. Companions like Ibn Umar, Ibn Mas'ud, and Anas confirm that the Prophet (peace be upon him) prayed two rak'ahs during his travels, and this practice continued with Abu Bakr, Umar, and Uthman. Consensus exists among scholars that shortening the four-rak'ah prayers to two is permissible for a traveler undertaking a distance customarily considered sufficient for shortening prayer, such as during Hajj, Umrah, or Jihad.