Musannaf Ibn Abi Shayba 23:213

'Affan narrated to us, he said: Hammad bin Salamah narrated to us, he said: Thabit informed me, from Anas bin Malik: That Abu Musa al-Ash'ari—or Anas—said: I saw in a dream as if I had taken many horses, and I led them until I reached a mountain. And behold, the Messenger of Allah (ﷺ) was atop the mountain, and Abu Bakr was at his side, and he began gesturing with his hand toward Umar. So I said: "Indeed we belong to Allah, and indeed to Him we shall return. By Allah, Umar has died." Then I said: "Will you not write to Umar about it?" He said: "I would not write to Umar announcing his own death."