أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ بُكَيْرِ بْنِ الأَخْنَسِ، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ فَرَضَ اللَّهُ الصَّلاَةَ عَلَى لِسَانِ نَبِيِّكُمْ صلى الله عليه وسلم فِي الْحَضَرِ أَرْبَعًا وَفِي السَّفَرِ رَكْعَتَيْنِ وَفِي الْخَوْفِ رَكْعَةً ‏.‏

It was narrated that Ibn Abbas said: "Allah (SWT) enjoined the prayer on the tongue of your Prophet (PBUH): four (rak'ahs) while a resident, two rak'ahs while traveling, and one rak'ah during times of fear." Translation Not Available

Book Ref: Sunan An Nisai Book 18 Hadith 1532
Web Ref:  Sunan An Nisai Vol 2 Book 18 Hadith 1533

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