One God, not three gods
The Bible begins with a firm confession: God is one. Israel was surrounded by nations that worshipped many gods, so Moses called God's people to love and worship the Lord alone (Deuteronomy 6:4-5). Christians have not set that conviction aside. Belief in the Trinity does not mean believing in three gods.
Instead, the word Trinity tries to hold together everything Scripture says. There is only one true God. Yet the Father is called God, Jesus the Son is spoken of and treated as divine, and the Holy Spirit acts and speaks as God. It can stretch our minds, and that's understandable. God is not a puzzle we can fully solve.
Hear, O Israel: The Lord our God is one Lord:
The Father, Son, and Spirit appear together
At Jesus' baptism, the Son is baptised, the Spirit comes down like a dove, and the Father's voice speaks from heaven (Matthew 3:16-17). They are not simply three names for one person taking turns. The scene presents the Father, Son, and Spirit in relationship with one another.
After rising from the dead, Jesus told his disciples to baptise people in the one name of the Father, and of the Son, and of the Holy Ghost (Matthew 28:19). Notice both parts of that statement. Jesus names all three, while speaking of one name. This became central to how Christians understood God and welcomed new believers.
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Jesus is more than a teacher
John opens his Gospel by describing the Word, who was with God and was God, and then identifies that Word as the one who became flesh in Jesus (John 1:1-3, John 1:14). Jesus is distinct from the Father, yet John does not describe him as a created messenger or merely a wise human teacher.
Jesus also spoke of the unique closeness between himself and the Father, saying that he and the Father are one (John 10:30). His listeners understood this as a claim with profound implications about his identity (John 10:31-33). Christians have differed over many details of theology, but historic Christianity has confessed Jesus as truly divine and truly human.
In the beginning was the Word, and the Word was with God, and the Word was God.
The Holy Spirit is personal and divine
The Holy Spirit is not presented as an impersonal force. Jesus promised that the Father would send another Comforter, the Spirit of truth, to be with his followers (John 14:16-17). The Spirit teaches, guides, strengthens, and points people towards Christ.
In the account of Ananias and Sapphira, Peter says that lying to the Holy Ghost is lying to God (Acts 5:3-4). Paul also closes his letter to the Corinthians by placing the grace of Jesus, the love of God, and the fellowship of the Holy Ghost together in a blessing (2 Corinthians 13:14).
So the Trinity is not a claim that every question has an easy answer. It is a way of listening carefully to the whole witness of Scripture. Read the passages for yourself, and let them lead you to worship the one God who saves, loves, and draws near.
The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen.