Sahih Muslim
The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness (Kitab Al-Dhikr)
Book Number: 035 / Hadith Number: 6580
Abu Huraira reported that Fatima came to Allah's Apostle (may peace be upon him) and asked for a servant and told him of the hardship of household work. He said: You would not be able to get a servant from us. May I not direct you to what is better than the servant for you? Recite Subhaana Allah thirty-three times, al- Hamdu li-Allah thirty-three times and Allah-o-Akbar thirty-four times as you go to bed. This hadith has been narrated on the authority of Suhail with the same chain of transmitters.