Musnad Ahmad 31:540

'Affan narrated to us, 'Abd al-Wahid narrated to us, al-A'mash narrated to us, from Abu Salih, from Abu Sa'id, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "To Allah, the Almighty and Majestic, belong one hundred mercies. He divided one part of them among the creation, and by it, people show mercy to one another, as do the wild beasts and the birds."