According to Hinduism scriptures, who created parabrahman?
Is parabrahman itself created parabrahman (self-creation)? Or is there any other entity created parabrahman?
Similar question was also asked by Gargi to Yagyavalkya, the scholar of vedas who defeated other Brahmin scholars in the courtyard of Janaka. This is what he answered
3.6.1 Then Gārgī, the daughter of Vacaknu, asked him. ‘Yājñavalkya,’ she said,
‘if all this is pervaded by water, by what is water pervaded?’ ‘By air, O Gārgi.’ ‘By what is air pervaded?’ ‘By the sky, O Gārgī.’ ‘By what is the sky pervaded?’ ‘By the world of the Gandharvas,1 O Gārgī.’ ‘By what is the world of the Gandharvas pervaded?’ ‘By the sun, O Gārgī.’ ‘By what is the sun pervaded?’ ‘By the moon, O Gārgī.’ ‘By what is the moon pervaded?’ ‘By the stars, O Gārgī.’ ‘By what are the stars pervaded?’ ‘By the world of the gods, O Gārgī.’ ‘By what is the world of the gods pervaded?’ ‘By the world of Indra, O Gārgī.’ ‘By what is the world of Indra pervaded?’ ‘By the world of Virāj, O Gārgī.’ ‘By what is the world of Virāj pervaded?’ ‘By the world of Hiraṇyagarbha, O Gārgī.’ ‘By what is the world of Hiraṇyagarbha pervaded?’
He said, ‘Do not, O Gārgī, push your inquiry too far, lest your head should fall off. You are questioning about a deity that should not be reasoned about. Do not, O Gārgī; push your inquiry too far.’ Thereupon Gārgī, the daughter of Vacaknu, kept silent.
Actually Brahman/Purusha/Hiranyagarbha(golden womb) is Swayambhu(self-born) omnipresent consciousness and is the cause of manifested reality and its divisions like intellect, mind and ego.
In the beginning this was Self alone, in the shape of a person (puruṣa). He looking around saw nothing but his Self (Atman). He first said, "This is I", therefore he became I by name. —Brihadaranyaka Upanishad 1.4.1
3.8.8. He said: O Gārgī, the knowers of Brahman say, this Immutable (Brahman) is that. It is neither gross nor minute, neither short nor long, neither red colour nor oiliness, neither shadow nor darkness, neither air nor ether, unattached, neither savour nor odour, without eyes or ears, without the vocal organ or mind, non-luminous, without the vital force or mouth, not a measure, and without interior or exterior. It does not eat anything, nor is It eaten by anybody.
3.8.11. This Immutable, O Gārgī, is never seen but is the Witness; It is never heard, but is the Hearer; It is never thought, but is the Thinker; It is never known, but is the Knower. There is no other witness but This, no other hearer but This, no other thinker but This, no other knower but This. By this Immutable, O Gārgī, is the (unmanifested) ether pervaded.
This question is valid for any sharp intellect, but there is no answer to this question in scriptures or by any enlightened beings except silence. So, if you are asking the cause of God/Brahman casually than its ok, but if you are seriously thinking about it everyday like some of the scholars of Vedas like Gargi than your head can explode as forewarned by Yagyavalkya because infinite Self cant be processed by a finite brain of mortal self. To process and understand even the cause/source of infinite, one will have to merge with infinite in Samadhi. If someone does find out the answer of this question in reality he would either disappear in infinite or even if he manages to return to physical reality, he cant use intellect or reasoning to express it, because intellect/knowledge is finite and concrete but Brahman is the cause of it all.
It would be like as explained by Ramkrishna Paramhansa
A salt doll wanted to measure the ocean’s depth. It wanted to be the first to tell how deep it was. But the moment it got into the water, it melted.
Man in Samadhi, knowing (becoming) Brahman goes beyond reason and is mute. No longer has he the power to describe the nature of Brahman.
No one has created Brahman. There is no beginning or end of Brahman. Only Jagat (universe) is what apparently created and destroyed.
Following is the the text from Chhandogya Upanishad constitutes the knowledge Aruna gave to his son Shwetaketu when he returned home after learning of 12 years:
VI-ii-1: 'In the beginning, dear boy, this was Being alone, one only, without a second. Some say that, in the beginning, this was Non-being alone, one only, without a second. From that Non-being arose Being.'
VI-ii-2: Aruni said, 'But now, indeed, dear boy, could it be so? How could Being arise from Non-being? In truth, dear boy, in the beginning (before creation), there was Being alone, one only, without a second.
That Brahman created all the things e.g five basic elements and other deities.
VI-ii-3: 'That Being willed, "May I become many, may I grow forth." It created fire. That fire willed, "May I become many, may I grow forth". It created water. Therefore whenever a man grieves or perspires, then it is from fire that water issues.
After creating the universe and bodies it itself entered into them as individual salves:
VI-iii-2: 'That deity willed, 'Well, let me, entering into these three deities through this living self (Jivatman), differentiate name and form.
So, No one created Brahman, all the things and forms are created by and from Brahman.
Your question "Is parabrahman itself created parabrahman (self-creation)?" can be answered using Aitareya Upanishad which also describes the creation in detail.
I-iii-13: Being born, He manifested all the beings; for did He speak of (or know) anything else? He realised this very Purusha as Brahman, the most pervasive, thus: "I have realised this".
After creation, Brahman entered into bodies to initiate the life and thought whether anything/anyone else exist and it realize itself that only Brahman does exist.
Brahma Sutras 2.3.9 (Swami Vieswarananda translator - https://www.wisdomlib.org/hinduism/book/brahma-sutras/d/doc64257.html):
Adhikarana summary: Brahman is not created
Brahma-Sutra 2.3.9: Sanskrit text and English translation.
असंभवस्तु सतः, अनुपपत्तेः ॥ ९ ॥
asaṃbhavastu sataḥ, anupapatteḥ || 9 ||
asaṃbhavaḥ—There can be no origin; tu—but; sataḥ—of the Sat (That which is); anupapatteḥ—as it does not stand to reason.
- But there can be no origin of the Sat (That which is i.e. Brahman), as it does not stand to reason.
[summary of Sankara's commentary] The question arises whether Brahman also is an effect like Akasa etc. In the Svetasvatara Upanishad there occurs the text: “Thou art born with Thy face turned to all directions” (Svet. 4. 3), which clearly states that Brahman is born. This view is refuted by the Sutra, which says that Brahman, which is existence itself, cannot be an effect, as It can have no cause. “And He has neither parent nor Lord” (Svet. 6. 9). Neither can non-existence be such a cause, for the Sruti says, “How can existence come out of non-existence?” (Chh. 6. 2. 2). Nor is it proper to say that existence is its own cause, for the effect must have some speciality not possessed by the cause. Brahman is mere existence without any distinction. We observe that only particulars are produced from the general, as different pots are from clay, and not vice versa. Therefore Brahman, which is existence in general, cannot be the effect of any particular thing. The fact that every cause is itself an effect of some antecedent thing is repudiated by the Sruti: “That great, birthless Self is undecaying” (Brih. 4. 4. 25), for it leads to a regressus in infinitum. So Brahman is not an effect, but is eternal.
Brahman means Absolute Existence. It always was, It always will be. It is uncreate.