What is the Biblical basis for the "one" in "the Trinitarian God is one being in three persons"?

The difficulty with this article written by Jacob Allee for CARM (20 June 2011) is that not one single verse from the Bible is given. Instead, the author uses a philosophical approach to show how the being of God is different to the being of a human. Here are the relevant quotes from his article:

The Bible teaches that within the one being that is God, there is a simultaneous existence of three coequal and coeternal persons;

[God] is also unique from human beings in that the totality of what God is contains three distinct persons as opposed to human beings who only have one person as part of their being.

God is one “being” who exists as three “persons,”

God is simply a different kind of being than human beings, containing more persons in His existence than humans.

Nowhere does he say that the three “persons” who make up the One Being of God are separate – distinct, yes, but not separate. This is what the Athanasian Creed [1] declares:

We worship one God in trinity and the Trinity in unity, neither confusing the persons nor dividing the divine being... And yet there are not three eternal beings, but one who is eternal; as there are not three uncreated and unlimited beings, but one who is uncreated and unlimited... Christian truth compels us to acknowledge each distinct person as God and Lord... and so we must worship the Trinity in unity and the one God in three persons.

Neither does he say that the Father, the Son and the Holy Spirit are three “beings”. Does he say “the persons of the Trinity are independently existing things”? If so, I can’t see it.

The Bible declares that there is only the One God (Deuteronomy 6:4; Galatians 3:20; Ephesians 4:5). The Hebrew word translated “one” in Deuteronomy 6:4 is ‘echad’. It means “unity,” not “singularity.” It is also used in Genesis 2:24 in referring to a husband and wife being “one” flesh. A husband and wife are not one as in a singular being. Rather, they are in unity with each other. There is a Hebrew word that means “absolute singularity,” ‘yachid’, but it is never used in the Hebrew Scriptures in reference to God.

Within the One Being of God subsists the three “persons” of the Father, the Son and the Holy Spirit. They are not “persons” in the sense that humans are persons, and this distinction is made clear in the article. I get the impression that Jacob Allee is not disagreeing with that in his article, although his wording could be clearer.

[1] https://www.gotquestions.org/Athanasian-creed.html

Trinitarian orthodoxy can be formulated on the basis of 3 sets of NT statements, each consisting of one primary and several supporting statements:

1. 'yet for us there is one God, the Father,' (1 Cor 8:6a)

"This is eternal life, that they may know You, the only true God," (Jn 17:3a)

Jesus answered, "The foremost [commandment] is, 'Hear this O Israel: The Lord our God, the Lord is one,'" (Mk 12:29)

[Here Jesus quoted the Shema: 'Shema Yisrael, YHWH eloheinu, YHWH echad.' (Deut 6:4).]

2. "I and the Father are one." (Jn 10:30)

[If Jesus was speaking in Hebrew, He probably said "Ani veha'av echad", ending with echad as in the Shema.]

In the beginning was the Word, and the Word was with God, and the Word was God. (Jn 1:1)

whose are the fathers, and from whom is the Christ according to the flesh, Who is God over all, blessed forever. Amen. (Rom 9:5)

Who, existing in the form of God, did not consider to be equal with God something to be grasped, (Phil 2:6)

No one has ever seen God. The only begotten God, the One who Is in the bosom of the Father, He has made Him known. (Jn 1:18)

Plus 5 passages where the Son is referred as "ho Theos" with a qualification: Mt 1:23; Jn 20:28; Tit 2:13; 2 Pet 1:1; 1 Jn 5:20.

3. The Son and the Father are really distinct personal subjects.

[While the above is not an NT statement, it is an unavoidable straightforward conclusion from many NT statements, such as:]

"You are My Son, the beloved; in You I am well pleased." (Mk 1:11b)

"For the Father loves the Son and shows Him all things that He does." (Jn 5:20a)

"As the Father knows Me, I also know the Father; and I lay down My life for the sheep." (Jn 10:15)

"But that the world may know that I love the Father, and as the Father has commanded Me, thus I do." (Jn 14:31)

"Now, Father, glorify Me together with Yourself, with the glory which I had with You before the world was." (Jn 17:5)

Correspondingly, there are 3 possible ways to fall from trinitarian orthodoxy, each by denying one of the statements:

• Denial that there is one God = tritheism
• Denial that the Son and the Father are one = Arianism
• Denial that the Son and the Father are really distinct = modalism or Sabellianism

Of those ways to fall, the first to occur historically was modalism (Sabellius fl. ca. 215), but it was Arianism which presented the biggest threat to orthodoxy and prompted the Church to elaborate a precise formulation of trinitarian doctrine.

Since Arians denied that the Son and the Father were one, they had to interpret Jesus' words "I and the Father are one." (Jn 10:30) in the sense of only moral oneness and not ontological oneness. To counter that eisegesis, the orthodox sought for the right word to add to Jn 10:30 to convey unequivocally the sense of ontological oneness: "I and the Father are one"... what?

We arrive at the same question from four key statements by Jesus of his divinity that were not mentioned above: the 4 times in which He explicitely applied to Himself the divine Name in the first person revealed in Ex 3:14: "Ehyeh", "Ego Eimí", I Am": Jn 8:24,28,58 & 13:19. If each of the Father and the Son names Himself "Ego Eimí", "I Am", then Each is a distinct "I" but Both are the same... what?

The natural answer to that question was the term ousía, which derived precisely from the verb "eimí", "to be". So, the initial orthodox answer to the Arian challenge was: the Father and the Son are one ousía and two prósōpa, one being and two persons.

Now, in contemporary language the term "being" is ambiguous, and in principle could convey the sense of either ousía or hypostasis (the latter as synonym of divine Person, as was officially used since 382), though it sounds more like the former, with which it is etymologically related.

My understanding is that the scriptures convey that three Divine Persons share one divine nature.

I and the Father are one. [John 10:30, Young's Literal Translation] . . .

. . . . expresses a shared nature but different personalities.

One could re-word this and say that three Divine Persons share one divine existence.

Fulness being an attribute of divine nature means that the divine nature is shared perfectly, in fulness.

And of His fullness (the Word made flesh) we all have received, and grace for grace.

[John 1:16, KJV]

For in him (Christ) dwelleth all the fulness of the Godhead bodily.

[Colossians 2:9, KJV]

But the word 'being', when it refers to 'human being', has a specific meaning in that human persons, although they share the characteristics of humanity do not actually share the same humanity, that is to say the same human body and the same human soul.

I think that this causes a confusion of wording.

So I therefore, myself, prefer to say that three Divine Persons share one divine existence.

That is to say, three Divine Persons, dwelling in a perfection of unity, co-exist in the fulness of one divine nature.

(This wording therefore expresses person, unity, being and nature.)

And I know that some word this as 'three Divine Persons share one divine essence'.

And in one Lord Jesus Christ, the Son of God, begotten of the Father [the only-begotten; that is, of the essence of the Father, God of God,] Light of Light, very God of very God, begotten, not made, consubstantial with the Father;

First Council of Nicea 325 - Wikipedia

Then, also :

... who, being in the form of God, thought it not robbery to be equal with God:

[Philippians 2:6 KJV]

Here, existence (being) nature (form) deity (God) and person (he) are seen together.

The Son of God exists (being) in the form or nature of deity. That is how his person exists and that is the form in which he exists : deity.

It is similar to the expression 'I am that I am' Exodus 3:14, which expresses the fact of existence (of being) - I am - and the mode of being or the form of being or the nature of being - that I am.

This existence, this form, he shares (equal with God) : it is an equivalent, an equal, mode of existence with God.

This form of being is a shared form of being - the form or nature in which he exists and which existence he shares : is deity.

It is one form of existence which is shared.

One mode of being - is shared.