John 1:1 - "In the beginning was the Word, and the Word was with God and the Word was God." - Saint John recalls the first verse of Genesis here, saying that at the time of creation, the Word, that is the Incarnate Word / Jesus, was already with God and was God.
John 1:14 - "The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only Son, who came from the Father, full of grace and truth."
1 John 5:7 - For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.
And he quotes Jesus:
John 10:30 - "I and the Father are one."
John 14:9 "...He that has seen me has seen the Father."
Here is some interesting reading.Explanations from all kinds of sources.
"What is the origin of the Trinity doctrine?
The New Encyclopædia Britannica says: “Neither the word Trinity, nor the explicit doctrine as such, appears in the New Testament, nor did Jesus and his followers intend to contradict the Shema in the Old Testament: ‘Hear, O Israel: The Lord our God is one Lord’ (
Deut. 6:4). . . . The doctrine developed gradually over several centuries and through many controversies. . . . By the end of the 4th century . . . the doctrine of the Trinity took substantially the form it has maintained ever since.”—(1976), Micropædia, Vol. X, p. 126.
The New Catholic Encyclopedia states: “The formulation ‘one God in three Persons’ was not solidly established, certainly not fully assimilated into Christian life and its profession of faith, prior to the end of the 4th century. But it is precisely this formulation that has first claim to the title
the Trinitarian dogma. Among the Apostolic Fathers, there had been nothing even remotely approaching such a mentality or perspective.”—(1967), Vol. XIV, p. 299.
In The Encyclopedia Americana we read: “Christianity derived from Judaism and Judaism was strictly Unitarian [believing that God is one person]. The road which led from Jerusalem to Nicea was scarcely a straight one. Fourth century Trinitarianism did not reflect accurately early Christian teaching regarding the nature of God; it was, on the contrary, a deviation from this teaching.”—(1956), Vol. XXVII, p. 294L.
According to the Nouveau Dictionnaire Universel, “The Platonic trinity, itself merely a rearrangement of older trinities dating back to earlier peoples, appears to be the rational philosophic trinity of attributes that gave birth to the three hypostases or divine persons taught by the Christian churches. . . . This Greek philosopher’s [Plato, fourth century B.C.E.] conception of the divine trinity . . . can be found in all the ancient [pagan] religions.”—(Paris, 1865-1870), edited by M. Lachâtre, Vol. 2, p. 1467.
John L. McKenzie, S.J., in his Dictionary of the Bible, says: “The trinity of persons within the unity of nature is defined in terms of ‘person’ and ‘nature’ which are G[ree]k philosophical terms; actually the terms do not appear in the Bible. The trinitarian definitions arose as the result of long controversies in which these terms and others such as ‘essence’ and ‘substance’ were erroneously applied to God by some theologians.”—(New York, 1965), p. 899."
Trinity LIBRARY