صَحِيحُ مُسْلِمٍ
Sahih Muslim 728 b
The Book of Prayer - Travellers
The virtue of the regular sunnah prayers before and after the obligatory prayers, and their numbers
حَدَّثَنِي أَبُو غَسَّانَ الْمِسْمَعِيُّ، حَدَّثَنَا بِشْرُ بْنُ الْمُفَضَّلِ، حَدَّثَنَا دَاوُدُ، عَنِ النُّعْمَانِ بْنِ سَالِمٍ، بِهَذَا الإِسْنَادِ مَنْ صَلَّى فِي يَوْمٍ ثِنْتَىْ عَشْرَةَ سَجْدَةً تَطَوُّعًا بُنِيَ لَهُ بَيْتٌ فِي الْجَنَّةِ .
Nu'man b. Salim reported with the same chain of transmitters: He who observed twelve voluntary rak'ahs, a house will be built for him in Paradise.
Sahih Muslim, 728 bSahihصحيح