Summary: There is one God, but three personal expressions of the one undivided, infinite, and eternal nature of God.
The Oneness of God
In Deuteronomy 6:4-5 we read a verse that every Jew has cherished the Shema Israel - (Shema Israel, Adonai Eloheinu, Adonai echad) "Hear, O Israel: The Lord our God, the Lord is one! You shall love the Lord your God with all your heart, with all your soul, and with all your strength. There is but one and only one God manifested in three distinct persons in perfect harmony. God’s whole and undivided essence belongs equally, eternally, simultaneously, and fully to each of the three Persons of the Godhead, so that the Father, Son, and Holy Spirit each is fully God while each is his own personal expression, in role and activity, of the one eternal and undivided divine essence. There is one God, but three personal expressions of the one undivided, infinite, and eternal nature of God. By "nature," the Father, Son, and Holy Spirit, each is equally God, and each is fully God, as each possesses fully the one undivided nature. Yet each is a different Person, and as such, each is different in role and position within the Godhead. The Father is supreme in authority, the Son under the Father, and the Spirit under the Father and the Son. Not three God’s but one God in three Persons, blessed Trinity.
I. The Triune Godhead
A. The Trinity is Scriptural.
1. F.F. Bruce said, "Let us not be misled by the foolish argument that because the term "Trinity" does not appear in the Scriptures, the doctrine of the Trinity is therefore unscriptural.”
2. The Eternal Godhead is revealed in the Word of God as one God existing in three persons; the Father, the Son, and the Holy Spirit. All three are co-eternal, co-equal and co-existent in attributes, power, nature and glory.
3. Genesis 1:26-27 “And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth. So God created man in his own image, in the image of God created He him; male and female created He them.
4. Deuteronomy 6:4 “"Hear, O Israel: The Lord our God, the Lord is one!”
5. Matthew 28:19 “Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit”
6. 2 Corinthians 13:14 “The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all. Amen.”
B. The Father is God
1. 1 Chronicles 17:13 “I will be his Father, and he shall be My son; and I will not take My mercy away from him, as I took it from him who was before you
2. Isaiah 9:6 that he is called the Everlasting Father. This passage however is referring to Jesus and refers to Him as being the father of salvation.
3. Psalm 89:24-26 “But My faithfulness and My mercy shall be with him, and in My name his horn shall be exalted. Also I will set his hand over the sea and his right hand over the rivers. He shall cry to Me, ’You are my Father, My God, and the rock of my salvation.’”