Abu Dawud Book 35, Hadith Number 4704.
Chapter : Not known.
Narated By AbuHurayrah : I heard the Apostle of Allah (PBUH) say: He then mentioned a tradition like it. This version adds: When they propound that, say: “Say Allah is one. Allah is He to Whom men repair. He has not begotten and He has not been begotten, and no one is equal to Him.” Then one should spit three times on his left side and seek refuge in Allah from Satan.