Musnad Ahmad 32:1831

Abdullah ibn Bakr narrated to us, Humaid narrated to us, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I entered Paradise and saw a palace of gold. I said: 'To whom does this palace belong?' They said: 'To a young man from Quraysh.' I thought that it was me, so I said: 'Who?' They said: 'Umar ibn al-Khattab.'"