Sayyidah Aisha (may Allah be pleased with her) said that the Noble Prophet (peace and blessings be upon him) used to pray thirteen rak'ahs at night; the witr and the two sunnah rak'ahs of Fajr were included in them.
Hadith Referenceاللؤلؤ والمرجان / كتاب صلاة المسافرين وقصرها / 427
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 19 كتاب التهجد: 10 باب كيف كان صلاة النبي صلی اللہ علیہ وسلم وكم كان النبي يصلي من الليل»
Brief Explanation
Including the witr, that is, he would perform ten rak‘ahs of tahajjud in sets of two. Then, by performing one rak‘ah, he would make all of them odd (witr). Thus, these eleven rak‘ahs were for tahajjud and witr. Then, by adding the two sunnah rak‘ahs of Fajr, the total became thirteen rak‘ahs. (Raaz)