Musannaf Ibn Abi Shayba 37:300

Ibn ‘Ulayyah narrated to us, from Hisham, from Ibn Sirin, who said: I saw Kathir ibn Aflah in a dream, and I said to him, "O son of Aflah, how are you?" He said, "We are well." He said: I said, "Are you the martyrs?" He said, "No, the slain of the Muslims are not martyrs, but we are the *nudaba* (the chosen/the mourned)."