[Machine] Abdullah bin Umar, O son of my brother, indeed Allah sent Muhammad, ﷺ , and we do not know anything except what we have seen the Messenger of Allah, ﷺ , doing. The shortening of prayer during travel is a Sunnah that the Messenger of Allah, ﷺ , established, and it was narrated by Al-Layth from Ibn Shihab from Abdullah bin Abu Bakr, and it was supported by a group narrating from Ibn Shihab, and they did not question its chain of narration.  

عَبْدُ اللهِ بْنُ عُمَرَ يَا ابْنَ أَخِي إِنَّ اللهَ ﷻ أَرْسَلَ مُحَمَّدًا ﷺ وَلَا نَعْلَمُ شَيْئًا فَإِنَّمَا نَفْعَلُ مَا رَأَيْنَا رَسُولَ اللهِ ﷺ يَفْعَلُ وَقَصْرُ الصَّلَاةِ فِي السَّفَرِ سُنَّةٌ سَنَّهَا رَسُولُ اللهِ ﷺ وَرَوَاهُ اللَّيْثُ عَنِ ابْنِ شِهَابٍ عَنْ عَبْدِ اللهِ بْنِ أَبِي بَكْرٍ وَأَسْنَدَهُ جَمَاعَةٌ عَنِ ابْنِ شِهَابٍ فَلَمْ يُقِيمُوا إِسْنَادَهُ