Abu Huraira reported God’s messenger as saying, "He who believes in God and the last day should honour his guest; he who believes in God and the last day should not annoy his neighbour ; and he who believes in God and the last day should say what is good, or keep silent." In a version instead of speaking of the neighbour he said, "He who believes in God and the last day should join ties of relationship."
(Bukhari and Muslim.)