Abu Dawud Book 2, Hadith Number 1340.
Chapter : On the number of rakahs of the prayer at night.
Narated By N/A : The above tradition has also been transmitted by Sa’id through a different chain of narrators to the same effect. Ibn Bashahar narrated the tradition like that of Yahya b. Sa’id. His version has: He the salutation in a way that we could hear it.