The Holy Trinity – Father, Son, and Holy Spirit, one God in three Persons – is the central mystery of Christian faith. While the Trinity is fully revealed in the New Testament, the Old Testament contains glimpses and foreshadowings of this truth. The Church Fathers teach that God unveiled the Trinity gradually. In other words, hints of the Son and Holy Spirit are present from the beginning, only to be clarified by Christ’s coming and the Spirit’s outpouring at Pentecost.

Early Christians, especially the Church Fathers, read the Old Testament in light of Christ. They saw in certain passages the triune nature of God shining through. These ancient commentators, Saints like St. Athanasius, St. Basil the Great, St. Gregory of Nyssa, and St. Gregory the Theologian (Nazianzus), found seeds of Trinitarian theology in the Hebrew Scriptures. They pointed to plural phrases spoken by God, mysterious divine appearances (theophanies), and personifications of God’s Word and Wisdom as evidence that the one God was never truly alone: He is Father with His Word and Spirit from eternity. Using accessible language and patristic insight, we will explore how key Old Testament passages hint at the Trinity, and how this understanding enriches Orthodox faith and spirituality.

From the very first chapter of Genesis, the Church Fathers discern a plurality of Persons within the one God. In the creation account we read: “Then God said, ‘Let Us make man in Our image, after Our likeness’” (Genesis 1:26). The Fathers marveled at this use of plural pronouns. St. Basil the Great exclaims, “Does not the light of theology shine in these words, as through windows? Does not the Second Person show Himself in a mystical way, without yet manifesting Himself fully?”

God says “Us” and “Our” – not to angels or to Himself alone, but, as Basil insists, to His co-worker in creation, “to Him by whom also He made the worlds”. In other words, the Father speaks to His Son and His Spirit. The plural “Let Us” reveals an intimate divine counsel within God, which the Fathers understood as the Holy Trinity consulting in love about the creation of mankind.

It is significant that Genesis 1:2 also mentions “the Spirit of God was hovering over the waters,” and creation unfolds by God’s Word (“And God said…”) – early clues that God’s Word and God’s Spirit were active in the beginning. The Psalmist later sings, “By the Word of the Lord the heavens were made, and by the Breath of His mouth all their host” (Psalm 33:6). The Greek word for “breath” is pneuma, the same word used for “Spirit.”

One of the most striking foreshadowings of the Trinity is the story of Abraham’s three visitors at the Oak of Mamre (Genesis 18:1–15). The patriarch Abraham is resting outside his tent when “the Lord appeared to him” in the form of three men standing before him. Abraham bows low and addresses them in the singular, “My Lord”, begging them to accept his hospitality. The narrative switches fluidly between referring to three persons and calling them “the Lord” (YHWH). The early Church Fathers saw this mysterious episode as a Old Testament vision of God in a triune form.

Saint Augustine in the West later wrote at length on this passage, asserting that “Abraham saw the Trinity in a figure”. In Eastern tradition, this event is so significant that it is iconographically depicted as the “Old Testament Trinity.” The most famous example is the icon of the Hospitality of Abraham painted by St. Andrei Rublev, where the three angelic figures around the table represent the Father, Son, and Holy Spirit in perfect harmony.

In Orthodox churches, this icon is simply called “The Trinity.” By showing three figures who look nearly identical and circle a chalice on the table, Rublev expressed unity in three (one divine essence in three Persons) without needing words. Abraham’s intuition to address them as one Lord foreshadowed how Christians approach the Triune God – three hypostases, one God.

It’s true that some early Fathers (like St. Justin Martyr) interpreted one of the three visitors as the pre-incarnate Christ accompanied by two angelic attendants. Justin argued that the “Lord” who spoke with Abraham was God the Son, visible and distinct from the unseen Father in heaven. Yet whether one sees this theophany as Christ with two angels or a symbolic apparition of the Holy Trinity, the Orthodox Church deeply cherishes this passage as a Trinitarian mystery. In our hymns and art, we treat Abraham’s three visitors as revealing one God in three Persons.

The fact that Genesis 18 uses singular and plural pronouns interchangeably when describing the Lord and the three men is seen as a deliberate hint that, as Augustine wrote, “they had a single substance despite the plurality of persons”. Abraham’s encounter thus becomes a prototype of how God can be triune and yet one – a reality fully revealed only in the New Covenant.

Another Old Testament thread that the Church Fathers followed to understand the Trinity is the personification of Wisdom in the Proverbs. In Proverbs 8, “Wisdom” speaks as a divine person who was with God before the world began: “The Lord created me at the beginning of His work… Ages ago I was set up, at the first, before the beginning of the earth… when He marked out the foundations of the earth, I was beside Him, like a master worker, and I was daily His delight” (Prov. 8:22–30). Who is this mystical Wisdom that co-labors with God and shares in His joy? The Christian Fathers unanimously answer: it is the Word of God, God the Son, our Lord Jesus Christ before He took flesh.

St. Athanasius, in battling the Arian heresy, made much of this passage. The Arians tried to use “The Lord created me…” to claim the Son was a created being. Athanasius clarified that Wisdom in Proverbs does indeed refer to Christ – “the power of God and the wisdom of God” (1 Cor 1:24) – but the term “created” is to be understood in context or as referring to Christ’s role in the created order. He wrote that the Son is not a creature by nature; rather, Scripture here speaks in a figure. If “created me” is read in light of the whole passage, we see Wisdom was “begotten before all things” (Prov. 8:25 in LXX) and was with God from everlasting.

Therefore the Church understood “Wisdom” to be a poetic description of the Son of God who was eternally generated from the Father, yet in the “economy” (the plan of salvation) is sent into the world. Athanasius taught that the Son, as Wisdom, participated with the Father in creation, and what Proverbs describes is essentially the Father’s begetting of the Son outside time and the Son’s cooperative work in creation.

Eastern Fathers like St. Gregory the Theologian rejoiced to identify Christ in these ancient words of Solomon. It confirmed that the Logos (Word) was active from the beginning, not a later addition. They also linked this Wisdom passage with St. John’s prologue: “In the beginning was the Word… all things were made through Him” (John 1:1-3). Just as Proverbs portrays Wisdom as the craftsman by God’s side, so John reveals the Word as the divine agent of creation.

Thus, whenever the Old Testament speaks of God’s Wisdom, Orthodox commentary often hears an echo of Christ. For example, when Wisdom is said to “build a house” in Proverbs 9:1, the Fathers see a prophecy of the Son assuming humanity (building for Himself a “house” which is the Virgin’s womb and His human nature). The Wisdom literature, in this way, provides a bridge between the one God of Israel and the unveiled Trinity of Christianity – it invites us to think of God’s Reason, Word, and Wisdom as with Him eternally.

Beyond subtle hints, the Old Testament also recounts direct appearances of God – theophanies – which the Fathers often ascribed specifically to God the Son (the second Person of the Trinity). A consistent early Christian interpretation was that whenever God appears in visible form or speaks audibly in the Old Testament, it is the pre-incarnate Christ manifesting, since God the Father is unseen and the Spirit usually works invisibly. Thus, many Fathers called these appearances “Christophanies.” Two classic examples are the mysterious Angel of the Lord and the Burning Bush encounter.

The “Angel of the Lord” (or Angel of Yahweh) appears multiple times – to Hagar in the wilderness (Genesis 16), to Abraham on Moriah (Genesis 22), to Moses in the Burning Bush (Exodus 3), to Joshua as captain of the Lord’s army (Joshua 5), and so on. This figure is paradoxical: called an “angel” (messenger) yet often speaks as God Himself in the first person, and people who see him exclaim they have seen God. The early Church was convinced this was not a created angel but a manifestation of God’s Word. St. Justin Martyr in his Dialogue with Trypho argues that the Angel of the Lord who spoke to Moses from the bush, saying “I AM the God of your fathers”, could only be the Logos, the Son of God – the one who mediates God’s presence.

Another example: in Daniel 3, a fourth figure “like a son of God” appears in the fiery furnace with the three young men – the Church has often identified that savior in the flames as an appearance of Christ alongside His faithful, a sign of the Emmanuel (God-with-us). All these theophanies collectively point to the truth that the one God can be present in multiple ways simultaneously – which fits perfectly with the revelation of Father, Son, and Holy Spirit.

The Angel of the Lord is not a created angel at all, but God’s Son carrying the Father’s message and accompanied by the Spirit. Thus, even ancient Israel did knew about “God the Son,” as they experienced His presence and mentioned him by name.

When the Prophet Isaiah was granted a vision of God’s throne, he heard the seraphim angels crying out one to another the famous hymn: “Holy, Holy, Holy is the Lord of hosts; the whole earth is full of His glory!” (Isaiah 6:3). In the Eastern Orthodox Church, this Trisagion (“Thrice-Holy”) is understood and worshipped as a declaration of the three-fold holiness of the one God – a hint of the Trinity’s perfection. The angelic hymn wasn’t saying “holy” once or twice, but three times in honor of the Father, Son, and Holy Spirit (and yet Lord is singular, indicating one Lord).

Many Fathers saw deep meaning here. They asked: “Why do the seraphim repeat ‘holy’ three times? Who taught them to glorify God in this triple way?” St. Basil answers that it was the Holy Spirit Himself who inspired their thrice-raised acclamation. “How could the Seraphim cry ‘Holy, Holy, Holy,’ were they not taught by the Spirit how often true religion requires them to lift their voice in this ascription of glory?” Basil writes. In other words, the angels’ worship reflects the tri-personal reality of God – a reality the Holy Spirit revealed to them.

Orthodox liturgy joins this angelic song at every Divine Liturgy (“Holy, holy, holy, Lord of Sabaoth…”). We take it upon our lips because we recognise we are praising Father, Son, and Holy Spirit – the Lord God of hosts. The Trisagion is thus both biblical and Trinitarian. In fact, an ancient Orthodox prayer (used at Pentecost) explicitly interprets it so: “Holy God (the Father)… Holy Mighty (the Son)… Holy Immortal (the Spirit)… have mercy on us.” While this exact formula is not in Isaiah, it shows how the Church connects the “thrice-holy” with the Trinity.

St. Gregory Nazianzen in one of his poems imagines the angels ceaselessly glorifying the Triune Light with their triple “holy” exclamation. And in Revelation 4:8, St. John sees heavenly beings likewise singing “Holy, holy, holy Lord God Almighty” eternally. One “Holy” for each Person, yet together one Lord – such is the mystery glimpsed by Isaiah. For the lay believer, it is enough to sense that God’s holiness is supremely perfect – raised to the third degree – and in that perfection the Church later understood the presence of Father, Son, Spirit.

Reading the Old Testament with the eyes of the Church, we find it shimmering with the hidden presence of the Holy Trinity. The Trinity is not an abstract mathematical puzzle (“3=1”); it is the living God whom Israel worshipped knowingly in shadows and whom we worship now in fullness. Eastern Orthodox tradition, drawing on the Fathers, loves to show how the “Old is the New concealed, and the New is the Old revealed.” Every key moment in the Old Testament – Creation, revelation, salvation – contains seeds that blossom in Christ. May we, enlightened by the Fathers and the Spirit, ever glorify the Unoriginate Father, His co-eternal Son, and the Holy Spirit – one God who called us from the beginning into His marvelous light. Amen.