كتاب صلاة المسافرين وقصرها
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The Book of Prayer - Travellers
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Chapter: 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
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باب اسْتِحْبَابِ رَكْعَتَيْ سُنَّةِ الْفَجْرِ وَالْحَثِّ عَلَيْهِمَا وَتَخْفِيفِهِمَا وَالْمُحَافَظَةِ عَلَيْهِمَا وَبَيَانِ مَا يُسْتَحَبُّ أَنْ يُقْرَأَ فِيهِمَا
Sahih Muslim 727 a

Ibn 'Abbas reported that the Messenger of Allah (ﷺ) used to recite in first of the two (supererogatory) rak'ahs of the dawn:

"Say: We believed in Allah and what was revealed to us..." verse 136 from Surah Baqara, and in the second of the two: "I believe in Allah and I bear testimony that we are Muslims" (iii. 52).
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا الْفَزَارِيُّ، - يَعْنِي مَرْوَانَ بْنَ مُعَاوِيَةَ - عَنْ عُثْمَانَ بْنِ حَكِيمٍ الأَنْصَارِيِّ، قَالَ أَخْبَرَنِي سَعِيدُ بْنُ يَسَارٍ، أَنَّ ابْنَ عَبَّاسٍ، أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَقْرَأُ فِي رَكْعَتَىِ الْفَجْرِ فِي الأُولَى مِنْهُمَا ‏{‏ قُولُوا آمَنَّا بِاللَّهِ وَمَا أُنْزِلَ إِلَيْنَا‏}‏ الآيَةَ الَّتِي فِي الْبَقَرَةِ وَفِي الآخِرَةِ مِنْهُمَا ‏{‏ آمَنَّا بِاللَّهِ وَاشْهَدْ بِأَنَّا مُسْلِمُونَ‏}
Reference : Sahih Muslim 727a
In-book reference : Book 6, Hadith 121
USC-MSA web (English) reference : Book 4, Hadith 1576
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