। ॥ ४३८ ॥
In plain words
The one who has realized — on the strength of what scripture itself declares — that his own Self is Brahman: that person is entirely free of the chains of worldly existence. That is the one called liberated while still alive.
Close to the Sanskrit
He by whom the Brahman-nature of the Self has been realized, on the strength of scripture — completely freed from the bondage of worldly existence, he is regarded as liberated-while-living.