Musnad Ahmad 944:33

Uthman ibn Umar—who is Ibn Faris—narrated to us, Yunus informed us, from al-Zuhri, from the son of Khuzaymah ibn Thabit al-Ansari, the possessor of the two testimonies, from his uncle: That Khuzaymah ibn Thabit al-Ansari saw in a dream that he was prostrating upon a forehead. He informed the Prophet, peace and blessings of Allah be upon him, of that. The Messenger of Allah, peace and blessings of Allah be upon him, lay down for him and said, "Your vision is true." So he prostrated upon the forehead of the Messenger of Allah, peace and blessings of Allah be upon him.