According to Osho, the very question ‘Who knows non-being?’ is invalid: to ask ‘who’ already assumes a remaining knower, which means non-being has not occurred. Non-being (nirvana) is not a bodily or experiential event; when it is, no subject remains to register it. Thus it cannot be known as an object, only realized by the cessation of the knower.
You can’t ask who knows nothingness, because when nothingness truly happens, there’s no one left to know it.