The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness (Kitab Al-Dhikr)
Muslim :: Book 35 : Hadith 6553
Abu Huraira reported that Fatima (the daughter of the Holy Prophet) came to Allah's Apostle (may peace be upon him) and asked for a servant. He said to her: Say:" O Allah, the Lord of the seven heavens" ; the rest of the hadith is the same.