Atithi Devo Bhav

It is the verse in the Taittiriya Upanishad that says "Matru devo bhava, Pitru devo bhava, Acharya devo bhava, Atithi devo bhava". Tithi in Sanskrit means a date. In ancient time when means of communication were limited and it was not possible to anticipate date of arrival of guest the word "Atithi" was coined to depict a visiting person who had no fixed date of arrival or departure. "Devo" means God and Bhav means Be/Is, literally meaning "Guest is God"