(v. 1) As stated earlier, the word Allah is the proper Name of God that shares an etymology with the Hebrew (in pluralis majestatis) Elohim (אֱלֹהִים), probably from the root a-li-ha (ألِهَ) meaning “to go to and fro in fear and perplexity” or from aleph-waw-lamed (אול), meaning “strength and power” and related to the Arabic Form II awwala (أول), “to interpret” or “find the origin of.” Ash’arite theologians offer the following brief definition of Allah: “A proper name denoting the Essence (which is) the Necessary Existent; the one deserving of all perfection and transcendent above all deficiencies” (علم على ذات الواجب الوجود، المستحق لجميع الكمالات المتنزه عن جميع النقاءص).
The Qur’an is confirming in principle that the God of Muhammad is the same God of the biblical prophets, including Abraham, Moses, and Jesus. The word Ahad (أحد) is taken by Suyuti as either a permutative (بدل) or a second predicate (خبر ثان), with Huwa as subject and the Exalted Expression (لفظ الجلالة), i.e. Allah, as first predicate.
Tantawi says that the Exalted Expression as predicate indicates the occasion of the surah’s Revelation (سبب النزول) in which a group of Jews approached the Prophet asking about the identity of his God – “Who is He (Huwa)?” This is described in detail by al-Wahidi. As discussed in chapter two, the pronoun Huwa, spelled ha-waw and meaning “He (is),” is close to the meaning of the enigmatic tetragrammaton (Shem HaMeforash) spelled yod-he-waw-he (יהוה), if we consider this to be the imperfect tense of the verb hawah (הוה), meaning to “to be,” thus “He is” (yihweh), and translated as ὁ ὤν ([“I am] He who is”) in the LXX (from the 1p sing. Ehyeh [Exo. 3:14]). According to the Mishnah, the Shem HaMeforash was only articulated in the Temple by the High Priest (HaCohen HaGadol) and was believed to be the most exalted Name of God, the actual Name of His Essence in distinction to “Allah/Elohim” which indicated His Essence. Thus Huwa, or Hahut (هاهوت) according to Ibn al-’Arabi, is believed to be al-Ism al-’Azam (الإسم الأعظم), the very Name of God’s Essence according to al-Razi.
To put it in Philonic terms, Allah (الله)/Elohim (אֱלֹהִים) = Ho Theos (ο θεος) while Huwa(هو)/Yihweh (יהוה) = Ho On (ὁ ὤν).
The usage of Ahad as opposed to Wahid (واحد) is intended to confirm the fundamental creedal statement of the Children of Israel (بني إسرائيل), i.e. the Shema of Deut. 6:4: “Hear O Israel! The Lord our God, the Lord is One (Echad)” (שְׁמַע יִשְׂרָאֵל יְהוָה אֱלֹהֵינוּ יְהוָה אֶחָֽד); and confirmed by Christ in Mark 12:29 (ἀπεκρίθη ὁ Ἰησοῦς ὅτι πρώτη ἐστίν ἄκουε Ἰσραήλ κύριος ὁ θεὸς ἡμῶν κύριος εἷς ἐστιν).
Also, while wahid denotes one numerically and thus does not negate the existence of other “ones,” ahad, being also anarthrous, denotes utter uniqueness, one of a genus. In addition, Ahad negates the henotheism of the pre-Islamic Arabs who certainly affirmed that Allah was Wahid, but also acknowledged the existence of lesser deities.
With respect to Christianity, the Qur’an repudiates the belief that God has a “Son” (ولد) in the Trinitarian sense by stating that “Allah is only One (واحد) God” (Q 4:171.5). Thus while Allah is numerically one (واحد), the term wahid also denotes His “internal oneness,” i.e. He is only one person (hypostasis; Arab. nafs; Heb. nefesh); there is no multiplicity in the godhead and He shares His Essence with no one and nothing else.
This is the heart of the Qur’an’s critique of Trinitarianism. There are not multiple hypostatic (personal) pre-eternals; the attributes (sifat) of God are not separate and distinct hypostatic entities. The usage of Ahad in this ayah (112:1), however, denotes God’s “external oneness” thus not allowing any creature to be the incarnation of that indivisible Essence (ousia) since He is transcendent of space, time, and materiality, contra both Incarnational Modalism (Monarchism) and Trinitarianism.
In this vein, Hosea (11:9) says: “Indeed I am God and not man” (כִּי אֵל אָֽנֹכִי וְלֹא־אִישׁ)
Source: Ustadz Ali Ataie