। ॥ ६६५ ॥
In plain words
"This — just this — is Being itself": with that the śruti opens, and then it speaks on. This is Being, solid through and through. This is Consciousness, solid through and through. This is ānanda, solid through and through.
Close to the Sanskrit
"This one indeed is Being alone" — thus having introduced it, the śruti speaks; and also: "This is a mass of Being, this is a mass of Consciousness, this is a mass of Bliss."