Many claim that the doctrine of the trinity was introduced only in the third century when the ecumenical councils had been held to put a framework for orthodox apostolic faith against the Arian and Nestorian heresies which led to the drafting of the creed of faith. However, when examined closely, the doctrine of the trinity was introduced way before that in the Old Testament.
The name that is used for God in the Old Testament is “אֱלֹהִ֔ים” pronounced “’ĕ·lō·hîm” and is usually referred to in the plural, although a singular verb is used sometimes. For example, the first chapter of Genesis states: “Then God said, “Let Us make man in Our image, according to Our likeness” (Genesis 1:26) The hebrew translation of “let us make” is “נַֽעֲשֶׂ֥ה” pronounced “na·‘ă·śeh” which indicates a plural subject. The same phrase was used when God decided to confuse the builders of the tower of Babel: “Come, let Us go down and there confuse their language, that they may not understand one another’s speech.” (Genesis 11:7) the word “נֵֽרְדָ֔ה” pronounced “nê·rə·ḏāh,” means “let Us go down”. It has been also noted in some other books in the Old Testament like the Book of Isaiah, “Also I heard the voice of the Lord, saying: “Whom shall I send, And who will go for Us?”” (Isaiah 6:8) using the word “לָ֑נוּ” pronounced “lā·nū”; which means “Us”. This has been always noted as an indication of the hypostasis of the trinity nature of God that is of one will.
Jewish Rabbis used the “Logos” or the word “Memra” also “Ma’amar” or “Dibbur,” in Hebrew, as well as the Holy Spirit “Ruach Ha Kodesh”, in their interpretations to the Old Testament .
“Memra” also “Ma’amar” or “Dibbur,” meaning “Logos”
In the Book of Jubilees 12:22, the word of God is sent through the angel to Abraham. In other cases it becomes more and more a personified agency: “By the word of God exist His works” (Ecclus. [Sirach] 42:15); “The Holy One, blessed be He, created the world by the ‘Ma’amar'” (Mek., Beshallaḥ, 10, with reference to Psalm 33. 6). Quite frequent is the expression that “You who have made the universe with Your word and ordained man through Your wisdom to rule over the creatures made by You” (Wisdom 9:1). The same expression is repeated in the Jewish daily prayers: “Who by Your words cause the evenings to bring darkness, who opens the gates of the sky by Your wisdom”; . . . “who by His speech created the heavens, and by the breath of His mouth all their hosts”; through whose “words all things were created” (Singer’s “Daily Prayer-Book,” pp. 96, 290, 292). So also in 4 Esdras 6:38: “Lord, You spoke on the first day of Creation: ‘Let there be heaven and earth,’ and Your word has accomplished the work”. “Your word, O Lord, heals all things” (Wisdom 16:12); “Your word preserves them that put their trust in You” (Wisdom 16: 26). Especially strong is the personification of the word in Wisdom 18:15: “Your Almighty Word leaped down from heaven out of Your royal throne as a fierce man of war.”
The Mishnah, with reference to the ten passages in the first chapter of Genesis beginning with “And God said,” speaks of the ten “ma’amarot” (= “speeches”) by which the world was created (Abot 5:1; comp. Gen. R. 4:2: “The upper heavens are held in suspense by the creative Ma’amar”). Out of every speech [“dibbur”] which emanated from God an angel was created (Ḥag. 14a). “The Word [“dibbur”] called none but Moses” (Lev. R. i. 4, 5). “The Word [“dibbur”] went forth from the right hand of God and made a circuit around the camp of Israel” (Cant. R. i. 13).
In the Targum:
In the Targum the “Memra” (i.e. “the Word”) figures constantly as the manifestation of the divine power, or as God’s messenger in place of God Himself, wherever the predicate is not in conformity with the dignity or the spirituality of the Deity.
Instead of the Scriptural “You have not believed in the Lord,” Targ. Deut. i. 32 has “You have not believed in the word of the Lord”; instead of “I shall require it [vengeance] from him,” Targ. Deut. 18:19 has “My word shall require it.” “The Memra,” instead of “the Lord,” is “the consuming fire” (Targ. Deut. 9:3; comp. Targ. Isa. 30:27). The Memra “plagued the people” (Targ. Yer. to Ex.32:35). “The Memra smote him” (II Sam. 6:7; comp. Targ. I Kings 18:24; Hos. 13:14; et al.). Not “God,” but “the Memra,” is met with in Targ. Ex. 19:17 (Targ. Yer. “the Shekinah”; comp. Targ. Ex. 25:22: “I will order My Memra to be there”). “I will cover thee with My Memra,” instead of “My hand” (Targ. Ex. 33:22). Instead of “My soul,” “My Memra shall reject you” (Targ. Lev. 26:30; comp. Isa. 1:14, 42:1; Jer. 6:8; Ezek. 23:18). “The voice of the Memra,” instead of “God,” is heard (Gen. 3: 8; Deut. 4:33, 36; 5:21; Isa. 6: 8; et al.). Where Moses says, “I stood between the Lord and you” (Deut. 5:5), the Targum has, “between the Memra of the Lord and you”; and the “sign between Me and you” becomes a “sign between My Memra and you” (Ex. 31:13, 17; comp. Lev. 26:46; Gen. 9:12; 17: 2, 7, 10; Ezek. 20:12). Instead of God, the Memra comes to Abimelek (Gen. 20:3), and to Balaam (Num. 23: 4). His Memra aids and accompanies Israel, performing wonders for them (Targ. Num. 23:21; Deut. 1:30, 33:3; Targ. Isa. 63:14; Jer. 31:1; Hos. 9:10 [comp. 11:3, “the messenger-angel”]). The Memra goes before Cyrus (Isa. 45:12). The Lord swears by His Memra (Gen. 21:23, 22:16, 24:3; Ex. 32:13; Num. 14:30; Isa. 45:23; Ezek. 20:5; et al.). It is His Memra that repents (Targ. Gen. 6:6, 8:21; I Sam 15:11, 35). Not His “hand,” but His “Memra has laid the foundation of the earth” (Targ. Isa. 48:13); for His Memra’s or Name’s sake does He act (Isa. 48:11; II Kings 19:34). Through the Memra God turns to His people (Targ. Lev. 26: 9; II Kings 18:23), becomes the shield of Abraham (Gen. 15:1), and is with Moses (Ex. 3:12; 4:12,15) and with Israel (Targ. Yer. to Num. 10:35, 36; Isa. 63:14). It is the Memra, not God Himself, against whom man offends (Ex. 14:8; Num. 14:5; I Kings 8:50; II Kings 19:28; Isa. 1:2,16; 45:3, 20; Hos. 5:7, 6:7; Targ. Yer. to Lev. 5:21, 6:2; Deut. 5:11); through His Memra Israel shall be justified (Targ. Isa. 45:25); with the Memra Israel stands in communion (Targ. Josh. 22:24, 27); in the Memra man puts his trust (Targ. Gen. 15: 6; Targ. Yer. to Ex. 14:31; Jer. 39:18, 49:11).
Memra also reflected Mediatorship.
Like the Shekinah (comp. Targ. Num. 23:21), the Memra is accordingly the manifestation of God. “The Memra brings Israel nigh unto God and sits on His throne receiving the prayers of Israel” (Targ. Yer. to Deut. 4:7). It shielded Noah from the flood (Targ. Yer. to Genesis 7:16) and brought about the dispersion of the seventy nations (Genesis 11:8); it is the guardian of Jacob (Gen. 28:20-21, 35:3) and of Israel (Targ. Yer. to Ex. 12:23,29); it works all the wonders in Egypt (Ex. 13:8, 14:25); hardens the heart of Pharaoh (Ex. 18:15); goes before Israel in the wilderness (Targ. Yer. to Ex. 20:1); blesses Israel (Targ. Yer. to Num. 23:8); battles for the people (Targ. Josh. 3:7; 10:14; 23:3). As in ruling over the destiny of man the Memra is the agent of God (Targ. Yer. to Num. 27:16), so also is it in the creation of the earth (Isa. 45:12) and in the execution of justice (Targ. Yer. to Num. 33:4). So, in the future, shall the Memra be the comforter (Targ. Isa. 66:13): “My Shekinah I shall put among you, My Memra shall be unto you for a redeeming deity, and you shall be unto My Name a holy people” (Targ. Yer. to Lev. 22:12). “My Memra shall be unto you like a good plowman who takes off the yoke from the shoulder of the oxen”; “the Memra will roar to gather the exiled” (Targ. Hos. 11:5,10). The Memra is “the witness” (Targ. Yer. 29:23); it will be to Israel like a father (l.c. 31:9) and “will rejoice over them to do them good” (l.c. 32:41). “In the Memra the redemption will be found” (Targ. Zech. 7:5). “The Holy Word” was the subject of the hymns of Job (Test. of Job, 12:3, ed. Kohler).
Philo of Alexandria was born 20 BC and died 50 AD had even interpreted Memra as the Logos before Saint John used this word in his Gospel “For there are, as it seems, two temples belonging to God; one being this world, in which the high priest is the divine word, his own firstborn son. The other is the rational soul, the priest of which is the real true man, the copy of whom, perceptible to the senses, is he who performs his paternal vows and sacrifices, to whom it is enjoined to put on the aforesaid tunic, the representation of the universal heaven, in order that the world may join with the man in offering sacrifice, and that the man may likewise co-operate with the universe. (1.216)”
The Holy Spirit “Ruah” רֽוּחַ־
The Holy Spirit is mentioned more than 200 times in the Old Testament. In the book of Judges on Othniel, the son of Kenaz: “The Spirit of the Lord came upon him, and he judged Israel.” (Judges 3:10) and also on Samson: “And the Spirit of the Lord came mightily upon him, and he tore the lion apart ” (Judges 14:6). “The Spirit of the Lord shall rest upon Him, The Spirit of wisdom and understanding, The Spirit of counsel and might, The Spirit of knowledge and of the fear of the Lord.” (Isaiah 11:2). And also in the book of Isaiah “Until the Spirit is poured upon us from on high, And the wilderness becomes a fruitful field” (Isaiah 32:15).
The Holy Spirit is mentioned more than 200 times in the Old Testament. In the book of Judges on Othniel, the son of Kenaz: “The Spirit of the Lord came upon him, and he judged Israel.” (Judges 3:10) and also on Samson: “And the Spirit of the Lord came mightily upon him, and he tore the lion apart ” (Judges 14:6). “The Spirit of the Lord shall rest upon Him, The Spirit of wisdom and understanding, The Spirit of counsel and might, The Spirit of knowledge and of the fear of the Lord.” (Isaiah 11:2). And also in the book of Isaiah “Until the Spirit is poured upon us from on high, And the wilderness becomes a fruitful field” (Isaiah 32:15).
The Triune God revelations in the Old Testament
God has been seen in revelations in the Old testament many times refuting the ideas that reject the capability of God to be seen and revealed. This of course supports the trinity doctrine because one of the hypostasis is the Word that became flesh.
Revelation to Hagar
For example, in Genesis 16, “Then she called the name of the Lord who spoke to her, You-Are- the-God-Who-Sees; for she said, “Have I also here seen Him who sees me?” Therefore the well was called Beer Lahai Roi;[g] observe, it is between Kadesh and Bered.” (Genesis 16:13-14) the scripture used the word “רָאִ֖יתִי” that means “have I seen”.
Revelation to Abraham
Genesis 18 “Then the Lord appeared to him” (Genesis 18:1) using the word “וַיֵּרָ֤א” pronounced “way-yê-rā” means appeared.
Revelation to Jacob
Genesis 32 “So Jacob called the name of the place Peniel: “For I have seen God face to face” (Genesis 32:30)
Revelation to Manoah and his wife
In the book of Judges “And Manoah said to his wife, “We shall surely die, because we have seen God!”” (Judges 13:22) using the word “רָאִֽינוּ׃” that means we have seen.
In conclusion, the Word, the Holy Spirit, and the Triune God are all mentioned in the Old Testament and Jewish religious texts foreshadowing what Lord Jesus revealed in the New Testament about the Triune nature of God.