Musannaf Ibn Abi Shayba 27:310

Abu al-Ahwas narrated to us, from Husayn, from Hilal ibn Yasaf, from Abdullah ibn Zalim, from Sa'id ibn Zayd, who said: I bear witness regarding nine that they are in Paradise, and if I were to bear witness regarding the tenth, I would be truthful. He said: I said, "And what is that?" He said: The Messenger of Allah (peace and blessings of Allah be upon him) was upon Hira, along with Abu Bakr, Umar, Uthman, Ali, Talha, al-Zubayr, Sa'd ibn Malik, and Abd al-Rahman ibn Awf. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Be firm, Hira, for there is upon you none but a Prophet, or a truthful one (Siddiq), or a martyr." He said: I said, "Who is the tenth?" He said: "I am."