If a person performs the Agnihotra sacrifice without knowing anything about the Vaiśvānara Self, it will be like offering oblations into ashes instead of the fire.
But he who performs the Agnihotra sacrifice with full knowledge of the Vaiśvānara Self is deemed to have offered oblations to all the worlds, to all beings, and to all selves.
Just as the cotton fibres of the iṣīkā grass are totally consumed when thrown into the fire, similarly all sins are consumed of one who performs the Agnihotra sacrifice with the knowledge of the Vaiśvānara Self.
Therefore, even if a person who knows the Vaiśvānara Ātman gives the remnants of his food after eating to a person who has no caste, that will be like his oblation offered to his own Vaiśvānara Self. Here is a verse on the subject:
Just as here in this world, when children are hungry, they go to their mother and beg for food, in the same way, all living beings beg that the Agnihotra sacrifice may be performed without any delay.