Prayer (Kitab Al-Salat): Details of Commencing Prayer
Dawud :: Book 3 : Hadith 891
Narrated Abdullah ibn Umar:
The Prophet (peace_be_upon_him) said: Both hands prostrate as the face prostrates. When one of you puts his face (on the ground) he should put his hands too (on the ground). And when he raises it, he should raise them too.