This hadith has been transmitted on the authority of Mu'tamir, reported on the authority of his father.
Sahih Muslim Book 50, Hadith 24
← Previous Hadith 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.

Sahih Muslim Book 50, Hadith 23 Next Hadith → Verily, Allah created, on the same very day when He created the heavens and the earth, one hundred parts of mercy. Every part of mercy is coextensive with the space between the heavens. and the earth and He out of this mercy endowed one part to the earth and it is because of this that the mother shows affection to her child and even the beasts and birds show kindness to one another and when there would be the Day of Resurrection, Allah would make full (use of Mercy).

Sahih Muslim Book 50, Hadith 25