And when by means of the real nature of his self he sees, as by a lamp, the real nature of Brahman, then having known the unborn, eternal god, who is beyond all natures, he is freed from all fetters.

In plain words: When a person uses his own true Self like a lamp to see Brahman, he comes to know the God who was never born and lasts forever. Knowing this God, he is freed from everything that binds him.