Sahih al-Bukhari 350
Narrated 'Aisha: the mother of believers:
Allah enjoined the prayer when He enjoined it, it was two Rakat only (in every prayer) both when in residence or on journey. Then the prayers offered on journey remained the same, but (the Rakat of) the prayers for non-travellers were increased.
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ صَالِحِ بْنِ كَيْسَانَ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ، قَالَتْ
" فَرَضَ اللَّهُ الصَّلاَةَ حِينَ فَرَضَهَا رَكْعَتَيْنِ رَكْعَتَيْنِ فِي الْحَضَرِ وَالسَّفَرِ، فَأُقِرَّتْ صَلاَةُ السَّفَرِ، وَزِيدَ فِي صَلاَةِ الْحَضَرِ ".
Classification
Sahih (Authentic)
References
Sahih al-Bukhari 350
Sahih al-Bukhari Vol. 1, Book of Prayer (Salat), Hadith 346