Scripture is abundantly clear that there is only one God.
God makes this truth about Himself a centerpiece of Israel’s testimony:
“Hear, O Israel! Yahweh is our God. Yahweh is One” (Deut 6:4).
“For I am God, and there is no other; I am God, and there is no one like Me” (Isa 46:9).
In the New Testament, Paul presents the Father and the Son at the same time He reaffirms that God is One.
“God our Savior . . . desires all men to be saved . . .. For there is one God, and one Mediator also between God and men, the man Christ Jesus” (1 Tim 2:3-5).
“We know . . . that there is no God but one. . . .There is but one God, the Father . . . and one Lord Jesus Christ . . .” (1 Cor 8:6).
“God is only one” (Gal 3:20).
Paul’s words reflect His conviction that three Persons preside over the universe as One.
“There is . . . one Spirit, . . . one Lord, . . . one God and Father of all Who is over all and through all and in all” (Eph 4:4-6).
So the Persons of the Trinity are one in essence; God is only one Being. There are not three Gods.
To know that there is one perfect, sovereign, infinite Being and Will is a reality on which our sense of security rests.
(Spotlight 11, Lesson 3 in Doctrine 101: Learning about God)