Muwatta Malik, Book 7, Hadith 264 (In-Book) ⓘ

Yahya related to me from Malik from Hisham ibn Urwa from his father that A'isha, umm al-muminin said, "The Messenger of Allah, may Allah bless him and grant him peace, used to pray thirteen rakas in the night and then would pray two rakas when he heard the adhan for the subh prayer."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي بِاللَّيْلِ ثَلاَثَ عَشْرَةَ رَكْعَةً ثُمَّ يُصَلِّي إِذَا سَمِعَ النِّدَاءَ بِالصُّبْحِ رَكْعَتَيْنِ خَفِيفَتَيْنِ ‏.‏