The Book of Prayer - Travellers
كتاب صلاة المسافرين وقصرها
Read the English translation first, with the original Arabic directly underneath.
It is recommended to pray two rak`ah for the sunnah of Fajr. And encouragement to pray them regularly, and to make them brief, and to persist in offering them, and clarifying what is recommended to recite therein
Yahya b. Yazid al-Huna'i reported:
I asked Anas b. Malik about shortening of prayer. He said: When the Messenger of' Allah (ﷺ) had covered a distance of three miles or three farsakh (Shu'ba, one of the narrators, had some doubt about it) he observed two rak'ahs.
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَمُحَمَّدُ بْنُ بَشَّارٍ، كِلاَهُمَا عَنْ غُنْدَرٍ، - قَالَ أَبُو بَكْرٍ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، غُنْدَرٌ - عَنْ شُعْبَةَ، عَنْ يَحْيَى بْنِ يَزِيدَ الْهُنَائِيِّ، قَالَ سَأَلْتُ أَنَسَ بْنَ مَالِكٍ عَنْ قَصْرِ الصَّلاَةِ، فَقَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا خَرَجَ مَسِيرَةَ ثَلاَثَةِ أَمْيَالٍ أَوْ ثَلاَثَةِ فَرَاسِخَ - شُعْبَةُ الشَّاكُّ - صَلَّى رَكْعَتَيْنِ .