حَدَّثَنَا شَيْبَانُ بْنُ فَرُّوخَ، حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا يَزِيدُ، - يَعْنِي الرِّشْكَ - حَدَّثَتْنِي مُعَاذَةُ، أَنَّهَا سَأَلَتْ عَائِشَةَ - رضى الله عنها - كَمْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي صَلاَةَ الضُّحَى قَالَتْ أَرْبَعَ رَكَعَاتٍ وَيَزِيدُ مَا شَاءَ .
Mu'adha asked 'A'isha (Allah be pleased with her) how many rak'ahs Allah's Messenger (PBUH) prayed at the forenoon prayer. She replied: Four rak'ahs, but sometimes more as he pleased. Translation Not Available
Book Ref: Sahih Muslim Book 6 Hadith 1549
Web Ref: Sahih Muslim Book 4 Hadith 719 a