। ॥ २६ ॥
In plain words
Between the two words tat and tvam, the relation is co-reference: both words name one and the same reality. Through that relation, the Vedānta texts establish identity with Brahman.
Close to the Sanskrit
Indeed, of the two words 'tat' and 'tvam', of the two, the relation is co-referentiality; by that, by the Vedānta texts, oneness with Brahman is established.