Abu Dawud Book 2, Hadith Number 1259.
Chapter : On lying after praying the two rakahs before the dawn prayer.
Narated By Abu Bakrah : I came out with the Prophet (PBUH) to offer the dawn prayer. When he passed by a sleeping man he called him for prayer or moved him with his foot. The narrator Ziyad said: This tradition has been reported to us by Abu al-Fadl.