كتاب الصلاة
2  
The Book of Prayer
And in another narration of al-Bukhari and Muslim, ['Aishah (RA)] narrated:
"He used to pray ten Rak'at (of prayer), and making it Witr by one Rak'at, and he used to pray the two (Sunnah) Rak'at of Fajr, so that it became thirteen Rak'at."
وَفِي رِوَايَةٍ لَهُمَا عَنْهَا: { كَانَ يُصَلِّي مِنْ اَللَّيْلِ عَشْرَ رَكَعَاتٍ, وَيُوتِرُ بِسَجْدَةٍ, وَيَرْكَعُ رَكْعَتَيْ اَلْفَجْرِ, فَتِلْكَ ثَلَاثُ عَشْرَةَ } 1‏ .‏


‏1 ‏- صحيح.‏ رواه البخاري (1140)‏، ومسلم (738)‏ (128)‏.‏

Sunnah.com reference : Book 2, Hadith 282
English translation : Book 2, Hadith 373
Arabic reference : Book 2, Hadith 378