Can I assume that you don't believe the apostle? He said there is "one" God, the Father.
He didn't say there is one God, the Father, Son, and Holy Spirit.
The NT says it in the following (see #2):
1) Redemption is a function of divinity.
The NT shows
three separate divine agents, Father, Son and Holy Spirit in the work of redemption/salvation:
a) Father, Son and Holy Spirit at its beginning (Lk 1:35), the inauguration of Jesus' public ministry
(Mt 3:16-17),
b)
the Holy Spirit completing the Father's work of redemption through the Son [Ac 2:38-39; Ro 8 (v.26); 1Co 12:4-13 (vv.4-6); Eph 1:3-14 (v.14), 2:13-22 (v.18), 2Th 2:13; 1Pe 1:2];
c)
the nly way to enter the kingdom of the Father is through faith in the Son and regeneration by the Holy Spirit (Jn 3:1-15 (vv.5,14-15).
2) The Father, Son and Holy Spirit are bracketed together as the triune name of God.
a) Note in Mt 28:13 that Jesus said this was the name (
singular) of the
one God with whom we enter into relationship.
b)
Paul used all three interchangeably in 1Co 12:4-6,
they are linked together in prayer for
divine blessing in 2Co 13:14, and
they are linked in pronouncement of
divine blessing in Rev 1:4-5.
3) The close connection in the NT between Father, Son and Holy Spirit show a co-equal relationship:
Paul says "
the Lord (Jesus) is the Spirit" (2Co 3:16-18), meaning the Spirit is
one with Jesus in the unity of the Godhead.
Jesus not only works in men through the Spirit, but the Son and Spirit are co-equal
divine beings.
To express that Christ worked
through Paul, he would never say, "The Lord
is Paul."
So Paul bears witness to the Spirit's place in the Godhead.
4) The NT shows the Holy Spirit to be a person.
It refers to him with the personal pronouns
he, him, his, with personal titles and with personal functions.
The NT shows him acting as a person:
speaking (Ac 8:29),
deciding (Ac 15:28),
forbidding (Ac 16:7),
testifying (Ac 5:32),
sending out missionaries (Ac 13:14),
interceding (Ro 8:26-27).
5) To believe God is Three-In-One is not to violate the word of the OT.
The OT forbid worship of false gods--gods other than, apart from or outside YHWH.
The Son and Holy Spirit are not other than, apart from or outside YHWH any more than his Word (Jn 1:1, 14, 18) or his breath are other than, part from or outside YHWH (Ge 1:2; Job 26:13, 32:8, 33:4, 34:14-15; Ps 33:6).