Chapter-4. Swami Sri Adi Sankaracharya - The Genius ( Sankara Jayanti ) :
But how could we transfer these objects that we would like to offer to the gods in the celestial region?
They are invisible!
The celestials are not known and they are not seen.
So sacrifices or Yajnas were instituted, and the holy fire, the sacred Agni became the secret messenger or the carrier of the oblations to the gods.
We say, "Agnaye svaha" and make offerings to the Supreme Messenger of the Divine Being, Agni.
May He be pleased.
In all the Havans and Yajnas, we will find the first deity to be invoked is Agni.
This ritual is called Agnisthapanam.
It is invocation of the celestial behind the principle of fire, or the divinity of fire, who is called Fire-god, Agnidevata.
He is first invoked and then He is told: "Please take this to Indra", "Please take this to Yama", "Please take this to Varuna", and so on.
He will carry our offerings to the particular deities who are addressed through the Mantras with the suffix 'Svaha', in the Yajnas.
To be continued ....