BG 17.22-24
That alms given at unfit place and time, and to unworthy persons, disrespectfully and contemptuously, that is declared of darkness. " Aum Tat Sat," this has been considered to be the threefold designation of the Eternal. By that were ordained of old Brâhmanas, Vedas and sacrifices. Therefore with the pronunciation of " Aum " the acts of sacrifice, gift and austerity as laid down in the ordinances are always commenced by the knowers of the Eternal.