Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1345
Narated By 'Aisha : The Apostle of Allah (pbuh) used to pray thirteen rak'ahs during the night, observing the witr prayer with nine (or as she said). He used to pray two rak'ahs while sitting and pray two rak'ahs of the dawn prayer between the adhan and the iqamah.