Musnad Ahmad 32:1085

'Abd al-Razzaq narrated to us, from Ma'mar, who said: Al-Zuhri said: And Anas ibn Malik informed me, saying: "When it was the day of Monday, the Messenger of Allah (peace and blessings of Allah be upon him) drew back the curtain of the chamber, and he saw Abu Bakr leading the people in prayer. He said: So I looked at his face, and it was as if it were a page of a Mushaf, and he was smiling. He said: We were about to be distracted in our prayer out of joy at seeing the Messenger of Allah (peace and blessings of Allah be upon him). Abu Bakr wanted to step back, but he signaled to him: 'Stay as you are,' then he let down the curtain, and he passed away on that very day." Then 'Umar stood up and said: "The Messenger of Allah (peace and blessings of Allah be upon him) has not died, but his Lord has sent for him just as He sent for Musa, so he remained away from his people for forty nights. By Allah, I truly hope that the Messenger of Allah (peace and blessings of Allah be upon him) will live until he cuts off the hands and tongues of men among the hypocrites who claim—or he said: who say—that the Messenger of Allah (peace and blessings of Allah be upon him) has died."