। ॥ ५ ॥
In plain words
Whoever holds the thought 'I am not' is saying of brahman — the one real thing — that it does not exist. Whoever knows 'I am' knows, all on his own, brahman itself.
Close to the Sanskrit
He who knows 'I am not' — that one knows the real brahman itself as 'it does not exist'. Knowing 'I am', that one himself knows brahman itself.