Musnad Ahmad 32:891

Yahya narrated to us, from Humayd, from Anas, from the Prophet, peace and blessings of Allah be upon him, who 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. They said: 'It is for Umar ibn al-Khattab.'"