Musnad Ahmad 30:2840

Waki’ narrated to us, from Sufyan, from Abu al-Zinad, from al-A’raj, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever believes in Allah and the Last Day, let him honor his guest. And whoever believes in Allah and the Last Day, let him speak good or remain silent."