आकाशादन्य आकाश आकाशस्य यथा न हि ।एकत्वादात्मनो नान्य आत्मा सिध्यति चात्मनः ॥ १० ॥
In plain words
Space has no second space inside it, no other space set apart from itself — there is no such thing. And since ātman is one, there is no other Self to be found apart from the Self. Look for a second one and nothing turns up.
Close to the Sanskrit
Just as, indeed, there is no other space of space, distinct from space — so too, because of the oneness of the Self, no other Self, distinct from the Self, is established.