Musnad Abu Ya'la al-Mawsili 219:17

Abu Nasr 'Abd al-Malik ibn 'Abd al-'Aziz al-Qushayri al-Tammar narrated to us, Hammad ibn Salamah narrated to us, from 'Asim, from Abu Salih, from Umm Habibah, she said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever prays twelve rak'ahs in a day, Allah will build for him a house in Paradise."