One of the mantras which captures, not only the essence of Advaita, but also the Vedas themselves, is Rig Veda 1.164.39 —
“To one who does not know the supreme syllable of the Rig Veda, in which, in heaven, all the devas have taken their seats, what use is the Rig Veda?”
The mantra also appears in Shvetashvatara Upanishad [1]. The Rig Veda gets its name from the type of mantras it contains, known as a ‘ric‘, which literally means “praise”. These mantras focus on invoking and worshipping devas. “To one who does not know the supreme syllable of Rig Veda,” means not knowing what is being worshipped and invoked, the syllable pervading every word of every mantra. The devas take ‘their seats’ in this syllable because it is their source. Knowing this syllable is to know, not only the source of the devas, but also what the entire Rig Veda is in praise (ric) of.
The supreme syllable is known as akshara, which also means “imperishable” — a (“without”) + kshara (“destruction”). This is simply one word for Brahman or the Self [2]. So, Rig Veda 1.164.39 is asking, “What use is the Rig Veda to one who has not realised Brahman?” In other words, what the Rig Veda’s mantras are devoted to the praise of remains a mystery without seeing it is Brahman which is worshipped throughout as “the one described in various ways” [3].
All the mantras, their words, syllables and their sounds, are expressions of Brahman and are indivisible from it. The Rig Veda is dedicated to the worship of Brahman because of the knowledge it is the nature and source of all things, including the Vedas themselves. The view that any person composed the Vedas is false as it implies a ‘doer’ separate from Brahman. It is for this reason that the Vedas are regarded as not having a human author.
When it is said that the Self is “all This”, it means there is nothing else. Therefore, perceiving something other than the Self is an imagination and falsehood. With the reality of Advaita, the truth is that the Vedas come from Brahman and are inseparable from it [4]. Their mantras are in praise it and have the designated purpose to contemplate what is being praised, what is present in every word, syllable and sound, and invoked within oneself.
Each name (deva) worshipped is simply a different way of worshipping Brahman [5]. One who realises Brahman sees that each deva is no different to themselves. Ensnared by ignorance, one worships thinking that they are different to the form of Brahman being worshipped [6].
[1] 4.8
[2] Katha Upanishad 2.15-16: “The word which all the Vedas celebrate…is Om. This syllable is Brahman. This syllable is supreme.”
[3] Rig Veda 1.164.46
[4] Brihadaranyaka Upanishad 4.5.7:
Whoever understands the Vedas as other than the Self, the Vedas have cast them out. Whoever understands beings as other than the Self, beings have cast them out. Whoever understands all as other than the Self, all has cast them out… these Vedas, these beings and all are the Self.
[5] Brihadaranyaka Upanishad 1.4.6:
When they say, “Worship to that one! Worship to another!”, every single deva is his creation and he himself is all the devas.
[6] Brihadaranyaka Upanishad 1.4.9