Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) said: "Whoever believes in Allah and the Last Day should honour his guest; whoever believes in Allah and the Hereafter should not harm his neighbour; and whoever believes in Allah and the Last Day should speak good or remain silent."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16663