Does the Holy Bible explicitly teach the doctrine of the Trinity?
Q180 · The Holy Trinity
The Holy Trinity is evident at the baptism of our Lord Jesus (John 1:27–33), which is the template for our own baptism in the name of the three Hypostases according to St. Matthew (Matt. 28:19). We also find this doctrine in St. Paul’s blessing in 2 Cor. 13:14. The three Hypostases are also mentioned in John 14:16; Eph. 2:18; and 1 Pet. 1:21–22.
The work and titles of both our Lord Jesus Christ and the Holy Spirit in the Holy Bible attest to their divinity.
From the Old Testament shines forth the threefold sanctification of “Holy, Holy, Holy,” found in the vision of Isaiah (6:3); and its connection to the phrase “who will go for Us?” (6:8). The three Hypostases are also evident in the Bible’s frequent use of the plural form of the name “Elohim” (plural) for God, sometimes even connecting it to God’s oneness: “Hear, O Israel: The Lord ( Jehovah ) our God ( Elohim ; plural), the Lord ( Jehovah ) is one” (Deut. 6:4). It is also used in certain phrases such as “And God ( Elohim ; plural) said ‘Let Us make man in Our image’” (Gen. 1:26), and again “Let Us go down and there confuse their language, that they may not understand one another’s speech” (Gen. 11:7).
The Old Testament prepared the world to believe in the Holy Trinity, but it did not expressly reveal the Trinity since most of the gentiles of the time were deeply mired in polytheism (the belief in many gods). The Israelites were drawn towards idolatry, and at times, worshipped the pagan gods and fell into their abominations, even after their victory over these same gentiles.
360 St. Gregory of Nazianzus, Oration 31.25–26 (NPNF II/7:325–326; PG 36:161).
God was preparing His people Israel for the incarnation of the Word of God among the Jews, who feared the Lord more than the tribes that surrounded them. Israel was distinguished in the Old Testament by the appearance of many pure and God-fearing people, as well as its many prophets who communicated divine revelations concerning the coming of the Savior of the world.