In the Shanti Parva of the Mahabharata, Bhishma teaches: Arāvapy ucitaṃ kāryam ātithyaṃ gṛham āgate. Chettum apy āgate chāyāṃ nopasaṃharate drumaḥ.
Hospitality must be shown even to an enemy who comes to one’s house. A tree does not withdraw its shade even from the one who comes to cut it down.