Musnad Ahmad 175:24

Abu al-Yaman narrated to us, he said: Shu'ayb informed us, from al-Zuhri, he said: 'Abd al-Rahman ibn Ka'b ibn Malik informed us, that Ka'b ibn Malik al-Ansari—and he is one of the three who were forgiven—used to narrate that the Prophet, peace and blessings of Allah be upon him, said: "The soul of the believer is but a bird that feeds upon the trees of Paradise, until Allah, Blessed and Exalted is He, returns it to its body on the day He resurrects it."