Is there later Commentary etc that has explained more of the Oneness and is it the feeling of Oneness or one-pointness of mind?
Can you please provide a sutta reference(s) so users know the context of your question?
for I’m devoted to oneness.
A monk, mindful, his mind well-released, contemplating the right Dhamma
at the right times,
on coming to oneness
should annihilate darkness," the Blessed One said.
“contemplating the right Dhamma
at the right times,
Oneness means one-pointed concentration and the role tranquillity plays with other factors in eradication of defilements.
"4 Not only does absorption attainment entail
the temporary removal of the hindrances, it also makes it much
more difficult for them to invade the mind on later occasions.85 On
emerging from deep concentration the mind is “malleable”, “workable”, and “steady”,86 so that one can easily direct it to seeing things “as they truly are”.—Analayo
Just as a surgeon must tranquillize the patient, so the hindrances can be operated on and removed when the mind is tranquil and they can be more easily seen.
It’s hard to know truly if it meant that only. Altought Nidessa I says
One delights in“jhāna, is intent on oneness, reveres the supreme good.”
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But what happens when Superiority,Equal,Inferior tendency is removed. When I am is removed.
“Oneness” can represent a few different words. In the linked verse, it’s ekatta, which is literally “oneness”. Similar terms include ekodibhāva, ekaggatā, ekāyana, etc.
As a rule, when we see “one” in a contemplative context, it refers to samādhi AKA jhanas. It’s language, though, so it can sometimes be a bit loose.
Another usage is in metaphysics, where the proposition “all is oneness” is rejected as extreme. This probably refers to such ideas as the Brahmanical unity of the self and the cosmos. These metaphysics, in turn, may be inspired and informed by jhanic experiences.
“One” also shows up in Khp 4: "What is the one? All sentient beings are sustained by food. "
(Trans: Ven. Sujato).
All conditioned beings depend not just on food in the usual sense, but are necessarily dependent on other nutriments, āhāra, to arise and temporarily manifest: food,
sense-impressions, volitional thought/kamma, and consciousness (viññana).
Ven. Nyanaponika Thera has a useful summary here: The Four Nutriments of Life: An Anthology of Buddhist Texts
Hope this is helpful.