The mantras are from the Taittiriya Upanishad, Shikshavalli I.20 that says: matrudevo bhava, pitrudevo bhava, acharyadevo bhava, atithidevo bhava. It literally means "be one for whom the Mother is God, be one for whom the Father is God, be one for whom the Teacher is God, be one for whom the guest is God." matrudevah, pitrudevah, acharyadevah, atithidevah are one word each, and each one is a Bahuvrihi samasta-pada.
