As with all religious groups that are “unitarian” in their theology (i.e., maintaining that God exists as one Person), Muslims reject the Trinity chiefly on the basis of their false notion as to what the doctrine actually teaches. As with Jehovah’s Witnesses and Oneness Pentecostals, Muslims see the Trinity as teaching three separate Gods. Thus, because of their misrepresentation of the doctrine, Muslims see Allah (Arabic for “God”) existing as one Person. Hence, naturally they reject the deity of Jesus Christ falsely concluding if Jesus were God, then, there would be more than one God. Mohammad’s misconception of the Trinity is quite evident, which can be seen in many passages of Islam’s most sacred book, the Koran:
O People of the Book! Commit no excesses in your religion: Nor say of Allah taught but the truth. Christ Jesus the son of Mary was (no more than) a messenger of Allah, and His Word, which He bestowed on Mary, and a spirit proceeding from Him: so believe in Allah and His messengers. Say not “Trinity”: desist: it will be better for you: for Allah is one Allah. . . . (Sura 4:171; Yusuf Ali’s translation; emphasis added).
They do blaspheme who say: Allah is one of three in a Trinity: for there is no god except One Allah. If they desist not from their word (of blasphemy), verily a grievous penalty will befall the blasphemers among them (Sura 5:73; Yusuf Ali’s translation).
Note: the Arabic term for [Holy] “Trinity” (al-thaaluuth al-aqdas) is not contained in the Koran. Because of his incorrect notion of the Trinity (as three gods), Ali added the term “Trinity” into the text. While some other translations do contain “Trinity” others though are consistent to the actual Arabic word translating it as “three” (e.g., Sura 5:73: “They have truly disbelieved those who say: Lo Allah is a third of three”).
Therefore, the verses referenced above in the Koran, do not actually condemn the doctrine of the Trinity: for, as indicated, there are no actual references to the “Trinity” in the Koran. They are speaking against tritheism (three Gods), and thus not Trinitarianism—one God revealed in three distinct co-equal, co-eternal, co-existent Persons. The condemnation of the belief in the tritheism mentioned in the Koran (as well as polytheism) is shared by both Muslims and Christians. Therefore, we need to show Muslims that claiming that the belief of the Trinity equals the belief in three Gods is a false claim that misrepresents the Trinity. In doing so; Christian-Muslim dialogue can progress a lot further.
So, before presenting the concept of the biblical doctrine of the Trinity to Muslims (or any other anti-Trinitarian group) you must first deal with the unitarian/unipersonal assumption: i.e., God existing as one Person. For this is the theological starting point of groups such as Muslims, Jews, Jehovah’s Witnesses, Oneness Pentecostals, etc. It must be emphasized over and over: The very foundation of the doctrine of Trinity is ontological Monotheism—one God by nature (cf. Deut. 6:4; Jer. 10:10-11.)
The 3 Biblical Truths of the Trinity
1: There is only one God.
2: There are three Persons or Selves that are presented as God: the Father, the Son and the Holy Spirit.
3: The three Persons are distinct from each other.
Conclusion: The three distinct Persons share the same nature or Being of the one God.
First Truth: Monotheism. God is presented as one Being – not one person.
Passages which speak on “one God” (e.g., Deut 6:4; Isa. 44:6-8; Mark 12:29-30; 1 Tim. 2:5 et al) reveal that God is one Being. However, unitarian groups such as Muslims, JWs, Oneness Pentecostals etc. read into “one” God as “one” person. Through the OT and NT,plural nouns, verbs, adjectives and plural prepositions are applied to the one God (cf. Gen. 1:26; 3:22; 11:7; Isa. 6:8; 54:5; Eccl. 12:1 [see Heb.] et al). Also, in places such as Gen. 19:24, we find Yahweh on earth acting on behalf of Yahweh in heaven (as we see in the NT where the divine Son interacts with God the Father (e.g., John 1:18; 6:37-39; 14:23; 16:28; 17:5; Heb. 1:8, 10-12).
Second truth: Scripture presents that Father, Jesus Christ and the Holy Spirit are God and worshiped as God.
1. Jesus is God (ho theos, “the God) and seen as the Yahweh of the OT: e.g., John 1:1-3; John 1:18; John 20:28; Colossians 2:9; Philippians 2:5-11; Titus 2:13 and 2 Peter 1:1 (see Granville Sharp’s Greek Grammar Rule #1); Hebrew 1:3; and esp. V. 8 and 10-12. Further, He was presented as the great “I am” (egō eimi); viz. at John 8:24, 28, 58; 13:19; 18:5, 6, and 8 (in light of places in the OT such as Deut. 32:39; Isa. 41:4; 43:10; 48:12 – where Yahweh is referred to as egō eimi, “I am” in LXX).
2. He was presented as the YHWH of the OT.
The NT authors clearly envisaged Jesus Christ as the Yahweh of the OT. Hence, they often cited OT passages referring to Yahweh and applied them to Jesus Christ: e.g., compare Joel 2:32 with Rom. 10:13; Isa. 6:8 with John 12:41; Ps. 102-25-27 with Heb. 1:10; Isa. 45:23-24 with Phil. 2:9-11; Isa. 8:12, 13 with 1 Pet. 3:14, 15; etc. (see also Jesus is Jehovah: Old Testament passages of Jehovah applied specifically to Jesus Christ in the NT).
3. Jesus is Creator: e.g., John 1:3; Col. 1:16-17; Heb. 1:2, 8-10.
4. Jesus claimed He was fully God: Although Jesus never literally stated, “I am God,” Jesus’ claims to deity were much stronger and clearer than if He had said, “I am God.” In fact, some of Jesus’ claims to deity were only used of Yahweh alone: John 5:17-18; John 10:26-33 (cf. Duet. 32:39; Isa. 41:4; 48:12; Ps. 95:7); the seven “I am” (egō eimi) affirmations stated at John 8:24, 28, 58; 13:19; 18:5, 6, and 8.
5. Jesus is worshiped in a “religious context” which was reserved for God alone (cf. Exod. 20:5): e.g., Dan 7:14; Matt. 14:33; 28:9; John 9:38; Heb. 1:6; Rev. 5:11-14.– See Christ Worshiped as God
6. Jesus possesses the SAME attributes as God the Father, for example:
- Creator (cf. John 1:3; Col. 1:16-17; Heb. 1:10-12)
- Raises the dead and gives them life: John 5:21: “For just as the Father raises the dead and gives them life, even so the Son also gives life to whom He wishes” (cf. John 6:37-40, 44).
- Omnipresent (cf. Matt. 28:20; John 14:23; 2 Cor. 13:5; Gal. 2:20).
- Omniscient (cf. John 2:24-25; 6:64; 16:30; 21:17).
- Omnipotent or all-powerful (cf. Matt. 8:27; 9:6; 28:18; Heb. 7:25).
- Eternal (Pre-Existing) (cf. Micah 5:2; John 1:1; 8:58; 17:5).
- Immutable (cf. Heb. 13:8).
To recap, Scripture then presents in the clearest way that Jesus Christ is God (yet distinct from the Father, cf. John 1:1b; 17:5), Creator, worshipped in a religious context, and possesses the same attributes as that of God the Father.
The Holy Spirit is God: e.g., Acts 5:3-4; the Holy Spirit also possesses the attributes of God:
- Eternal, having neither beginning nor end (cf. Heb. 9:14),
- Omnipresent, being everywhere at the same time (cf. Ps. 139:7).
- Omniscient, understanding all things (cf. 1 Cor. 2:10-11).
- Omnipotent (cf. Luke 1:35).
The Holy Spirit is a Person: e.g., the Holy Spirit communicates (e.g., Acts 10:19-20; 13:2; Heb. 3:7-11; 10:15-17); personal pronouns (“I,” “He”) are applied to Him (cf. Acts 10:20; John 16:13-14); possesses “personal” attributes (e.g., He has a will [cf. 1 Cor. 12:9-11]; emotions [cf. Eph. 4:30]; intelligence in that He investigates [cf. 1 Cor. 2:10-11; Rom. 8:27]; He intercedes/prays [cf. Rom. 8:26]; He can be lied to [cf. Acts 5:3]; He can be blasphemed [cf. Mark 3:29-30]; He issues commands [cf. Acts 13:4; Acts 16:6]; He gives love [cf. Rom. 15:30]). See also: God the Holy Spirit: The Third Person of the Trinity
Third Truth: The three Persons are distinct from each other: e.g., John 1:1b. 17:5; Matt. 28:19; 1 Cor. 13:14; 1 John 1:3; Rev. 5:13. See also: Grammatical Details.
As mentioned, additionally, in the OT, God is presented as multi-Personal: e.g., Gen. 19:24; Isa. 48:16; Hosea 1:7; Eccl. 12:1 (Heb. “Creators”); Isa. 54:5 (Heb. “Makers”; see also: The Multi-Personal God in the Old Testament and Oneness Theology)
In conclusion then, Scripture presents a tri-personal God. The Trinity is God’s highest revelation to mankind. In John 4:23-24, Jesus told the Samaritan woman that God seeks those who worship Him “in spirit and truth.” In truth, God is triune. Worshiping a unipersonal God or three separate Gods is not worshiping Him in truth. The issue being that the truth of the Trinity, the self-disclosure of God to men, is found in nearly every page of the Holy Scriptures: There is one God, and there are three distinct, coequal, coeternal, and coexistent, self-cognizant divine Persons or Egos that share the nature of the one God—the Father, the Son, and the Holy Spirit.
 Historically, these verses are no doubt referring to a heretical so-called Christian sect called Mariyama or Collyridians who existed within the same geographical location and period as that of Mohammad. This sect held to a form of Tritheism, worshipping Mary and her Son both of which were believed to be two separate gods besides God.
 Specifically, Matt. 28:19; 1 Cor. 13:14; 1 John 1:3; and Rev. 5:13 (and there are many others) distinguish the Persons in the Trinity. This is due to their grammatical construction—namely, the repetition of both the article (ho, “the”) and conjunction (kai, “and”). For example, note the literal reading of 2 Cor. 13:14: “The grace [of] the Lord Jesus Christ, and the love [of] the God, and the fellowship [of] the Holy Spirit, be with all of you.” Or the literal reading of Rev. 5:13: “[to] the one sitting upon the throne and [to] the Lamb. . . .” Here, the Father (“the one sitting”) and Christ (“the Lamb”) are personally differentiated by the repetition of the article “the” (ho) and conjunction “and” (kai).