Musannaf Ibn Abi Shayba 27:595

Muhammad ibn Abi Ubaydah narrated to us, he said: My father narrated to me, from al-A’mash, from al-Qasim ibn Abd al-Rahman, from his father, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I have certainly seen myself as the sixth of six, there being no Muslim on the face of the earth other than us."