Musnad Ahmad 32:86

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There will come to you people whose hearts are more tender than yours." He said: Then the Ash‘aris arrived, among whom was Abu Musa al-Ash‘ari. When they drew near to Medina, they were chanting: Tomorrow we shall meet the beloved, Muhammad and his party.