। ॥ १२ ॥
In plain words
Like Ākāśa—space itself—That pervades all, peaceful in its very nature. It is the supreme light, without shape, the one truly worthy of being chosen. It has neither beginning nor end; it is supreme and bears the name Śaṅkara. It is to be realized within. That alone I am.
Close to the Sanskrit
That which, like Ākāśa—space—pervades everywhere, peaceful in nature; the supreme light, formless, most excellent; that which is without beginning or end, supreme, called Śaṅkara; that which is to be realized within—that alone I am.