Musnad Abu Ya'la al-Mawsili 115:73

'Abd al-A'la narrated to us, Yazid ibn Zuray' narrated to us, Sa'id narrated to us, from Qatadah, from Anas: That the Prophet of Allah (may Allah bless him and grant him peace) narrated that when he was ascended to the heaven, he said: "I came upon Idris in the fourth heaven."