Valmiki Ramayana Aranya Kanda Sarga 12 Shloka 29

अग्निम् fire, हुत्वा after making an offering, अर्घ्यम् water, प्रदाय after providing, अतिथिम् guest, प्रतिपूजयेत् should worship, काकुत्स्थ O Rama, अन्यथा otherwise, समुदाचरन् by adopting, तपस्वी the sage, दुःसाक्षीव like a false witness, परे लोके in other world, स्वानि his own, मांसानि flesh, भक्षयेत् will have to eat.

O scion of the Kakutstha dynasty, only after offering oblations to the Firegod, a guest should be worshipped with water etc. Otherwise the host will have to eat his own flesh in the other world like a false witness.