Kenn Maly says the Sache is emerging. Heidegger said Parmenides says so in the first line of fragment 6.
ἔστι γὰρ εἶναι
Is: that is to say, being.
The saying refers to being, not to beings. Being is. Heidegger hesitates on this, because one can say "it is" only of beings. Being precisely is not. But Parmenides says here: Being/das Sein is. Heidegger ask: are we capable of hearing this Greek word, that speaks of ἔστι and εἶναι, with a Greek ear? Or: Do we think the Greek saying of the words ἔστι and εἶναι in a Greek way? Finally, in using the words "is" and "being," do we think precidely enough at all?
Thought in its Greek way, the word εἶναι says: anwesen/to emerge. This verb speaks more precisely. It brings us, in a greater revealing, closer to the Sache to be thought. In accordance with this we must render ἔστι γὰρ εἶναι as: anwest nämlich anwesen: emerges, that is to say emerging. [P. 405]
What is being thought here is not being in its difference from beings, but rather only emerging: being as emerging, or simply, emerging itself.
The word of Parmenides that names this Sache is τὁ ἐόν. Heidegger says τὁ ἐόν as anwesend: anwesen selbst or anwest nämlich anwesen (energing: the emerging itself; or unfolding: the unfolding itself, emerges). That is to say emerging; unfolds, that is to say unfolding--emerges emerging.