। ॥ १४३ ॥
In plain words
The one by which everything else is known — by what could you ever know that one? So say the Upaniṣads: the Self, in the end, can only be reached by the Self.
Close to the Sanskrit
That by which [everything] is known — by what, indeed, could one know that? Thus is the statement of the Upaniṣads: the Self, therefore, is bound [only] by the Self.