He may permit something in His Book with a condition, and He may permit that thing on the tongue of His Prophet, peace and blessings be upon him, without that condition by which He permitted it in the Book. For Allah, exalted is His mention, only permitted in His Book the shortening of the prayer when they travel in the land in fear that the disbelievers may persecute the Muslims. Yet Allah, mighty and majestic, permitted, on the tongue of His Prophet, peace and blessings be upon him, the shortening (of the prayer) even if they do not fear that the disbelievers may persecute them, with the evidence that the shortening during travel is a permission, not an obligation, that they must shorten the prayer.

Ya'la bin Umayyah narrates that I said to Sayyiduna Umar bin Khattab (may Allah be pleased with him) that I am surprised at people shortening the prayer, even though Allah Almighty has said «‏‏‏‏فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُوا مِنَ الصَّلَاةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُوا» ‏‏‏‏ [ سورة النساء: 101 ] "And if you fear that the disbelievers may put you in trial, then there is no blame or sin upon you in shortening the prayer." And now this fear has ended. So Sayyiduna Umar (may Allah be pleased with him) said that I was also surprised at the same thing that you are surprised at, so I mentioned this matter before the Messenger of Allah (peace and blessings be upon him), and he said: "This is a charity which Allah Almighty has bestowed upon you as a mercy, so accept His charity (and benefit from this concession)."