It is narrated from Sayyiduna Zayd bin Khalid al-Juhani (may Allah be pleased with him) that he heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever believes in Allah and the Last Day, let him speak good or remain silent; and whoever believes in Allah and the Last Day, let him honour his neighbour; and whoever believes in Allah and the Last Day, let him honour his guest. Hospitality is three nights; whatever is beyond that is charity."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5168