The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness (Kitab Al-Dhikr)
Muslim :: Book 35 : Hadith 6517
Mus'ab b. Sa'd reported that his father told him that he had been in the company of Allah's Messenger (may peace be upon him) that he said: Is one amongst you powerless to get one thousand virtues every day. Amongst those who had been sitting there, one asked: How one amongst us can get one thousand virtues every day? He said: Recite:" Hallowed be Allah" one hundred times for (by reciting them) one thousand virtues are recorded (to your credit) and one tbousand vices are blotted out.