Musnad Ahmad 28:591

Qutaybah ibn Sa'id narrated to us, Rashdin informed us, from al-Hajjaj ibn Shaddad, from Abu Salih al-Ghifari, from 'Abdullah ibn 'Amr ibn al-'As, that the Prophet, peace and blessings of Allah be upon him, said: "The first to enter through this door is a man from the people of Paradise." Then Sa'd ibn Abi Waqqas entered.