Musnad Ahmad 788:134

'Affan narrated to us, Hammad—meaning Ibn Salamah—narrated to us, 'Asim informed us, from Abu Burdah, from Abu Musa, that the Prophet, peace and blessings of Allah be upon him, used to be guarded by his companions. I stood up one night and did not see him in his sleeping place, so what had passed and what was to come [of anxiety] seized me. I went to look, and there I was with Mu'adh, who had encountered what I had encountered. We heard a sound like the rumbling of a millstone, so we stood in our places. Then the Prophet, peace and blessings of Allah be upon him, came from the direction of the sound and said: "Do you know where I was and what I was in? A comer came to me from my Lord, the Almighty and Majestic, and gave me the choice between half of my nation entering Paradise and [the granting of] intercession, so I chose intercession." They both said: "O Messenger of Allah, supplicate to Allah, the Almighty and Majestic, to make us among those in your intercession." He said: "You, and whoever died not associating anything with Allah, are in my intercession."