Sahih Al Bukhari Hadith Number 1164

Narrated `Aisha: Allah’s Messenger (peace be upon him) used to offer thirteen rak`at in the night prayer and on hearing the Adhan for the morning prayer, he used to offer two light rak`at.

19  Prayer at Night (Tahajjud)
Hadith number 1164
Volume no 2
Chapter: 27 ( To offer two Rak’at before the Fajr prayer)