Sahih Muslim
The Book Pertaining to Repentance and Exhortation to Repentance (Kitab Al-Tauba)
Book Number: 037 / Hadith Number: 6632
Salman Farisi reported Allah's Messenger (may peace be upon him) as saying: Verily, there are one hundred (parts of) mercy for Allah, and it is one part of this mercy by virtue of which there is mutual love between the people and ninety-nine reserved for the Day of Resurrection.