Scripture reveals one God eternally existing in three co-equal, co-eternal persons: Father, Son, and Holy Spirit. While the word 'trinity' does not appear, the doctrine is built from passages affirming both God's oneness and the full deity of Father, Son, and Spirit.
Matthew 28:19
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Baptizing 'in the name [singular] of the Father, and of the Son, and of the Holy Ghost' — classic trinitarian formula.
And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:
Jesus' baptism: Son in the water, Spirit descending as a dove, Father's voice from heaven.
Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
Jesus prays the Father to send the Spirit — all three persons distinguished.
Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
Elect according to foreknowledge of God the Father, through sanctification of the Spirit, unto obedience of Jesus Christ.
Whiles it remained, was it not thine own? and after it was sold, was it not in thine own power? why hast thou conceived this thing in thine heart? thou hast not lied unto men, but unto God.
Lying to the Holy Ghost equated with lying to God — affirming the Spirit's deity.
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 creepeth upon the earth.
'Let us make man in our image' — plural divine self-reference.