Abu Karimah (may Allah be pleased with him) heard the Prophet (peace and blessings be upon him); he (peace and blessings be upon him) was saying: "Hosting (a guest) for the night is an obligation on every Muslim, and whoever the guest spends the morning with, it is an obligation upon him to host him" — or he said: "it is a debt upon him; if he (the guest) wishes he may claim it, and if he wishes he may leave it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18694