Musnad Ahmad 30:458

Abu Kamil narrated to us, Hammad narrated to us, from Abu Imran al-Jawni, from a man, from Abu Hurairah: That a man complained to the Messenger of Allah, peace and blessings of Allah be upon him, about the hardness of his heart. He said to him: "If you want your heart to soften, then feed the needy, and wipe the head of the orphan."