The one true God has revealed Himself as the eternally self-existent "I AM," the Creator of heaven and earth and the Redeemer of mankind. He has further revealed Himself as embodying the principles of relationship and association as Father, Son and Holy Spirit.
The terms "Trinity" and "persons," while not found in the Scriptures, are words in harmony with Scripture, whereby we may convey our understanding of the doctrine of Christ respecting the Being of God. We may therefore speak with propriety of the Lord our God who is One Lord, as a trinity or as one Being of three persons, and still be absolutely scriptural.
Christ taught a distinction of Persons in the Godhead which He expressed in specific terms of relationship — as Father, Son, and Holy Spirit — but that this distinction and relationship, as to its mode, is inscrutable and incomprehensible, because unexplained.
There is that in the Father which constitutes Him the Father and not the Son; there is that in the Son which constitutes Him the Son and not the Father; and there is that in the Holy Spirit which constitutes Him the Holy Spirit and not either the Father or the Son. The Father is the Begetter, the Son is the Begotten, and the Holy Spirit is the one proceeding from the Father and the Son. Because these three persons in the Godhead are in a state of unity, there is but one Lord God Almighty and His name one.
Deuteronomy 6:4 · Isaiah 43:10–11 · Matthew 28:19 · Luke 3:22 · John 1:18 · John 15:26 · 2 Corinthians 13:14