Sahih Muslim
The Book Pertaining to Repentance and Exhortation to Repentance (Kitab Al-Tauba)
Book Number: 037 / Hadith Number: 6629
Abu Huraira reported: I heard Allah's Messenger (may peace be upon him) as saying: Allah created mercy in one hundred parts and He retained with Him ninety-nine parts, and He has sent down upon the earth one part, and it is because of this one part that there is mutual love among the creation so much so that the animal lifts up its hoof from its younc, one, fearing that it might harm it.