The word "trinity" is not found in the Bible. Nevertheless, it is a word used to describe one fact the Bible teaches about God: Our God is a Trinity. This means there are three persons in one God and not three Gods. The persons are known as the Father, the Son, and the Holy Spirit; and they have all always existed as three distinct persons. The person of the Father is not the same person as the Son. The person of the Son is not the same person as the Holy Spirit. The person of the Holy Spirit is not the same person as the Father. If you take away any one, there is no God. God has always been a trinity from all eternity: "From everlasting to everlasting, You are God." (Psalm 90:2).
God is not one person who took three forms, i.e., the Father who became the Son, who then became the Holy Spirit. This belief is known today as the "Jesus Only Movement (also known as Oneness Pentecostalism)." It is taught by the United Apostolic and United Pentecostal churches and is an incorrect teaching.
Nor is God only one person as the Jehovah's Witnesses, the Way International, and the Christadelphians teach. (These groups are classified as non-Christian cults). For proof that there is more than one person in the Godhead, see the Plurality Study.
The Bible says there is only one God. Yet, it says Jesus is God (John 1:1,14); it says the Father is God (Phil. 1:2); and it says the Holy Spirit is God (Acts 5:3-4). Since the Son speaks to the Father, they are distinct persons. Since the Holy Spirit speaks also (Acts 13:2), He is a distinct person. There is one God who exists in three persons.
The following chart should help you understand how the Trinity doctrine is derived:
T H E T R I N I T Y
|Called God||Phil. 1:2||John 1:1,14; Col. 2:9||Acts 5:3-4|
|Creator||Isaiah 64:8; 44:24||John 1:3; Col. 1:15-17||Job 33:4, 26:13|
|Resurrects||1 Thess. 1:10||John 2:19, 10:17||Rom. 8:11|
|Indwells||2 Cor. 6:16||Col. 1:27||John 14:17|
|Everywhere||1 Kings 8:27||Matt. 28:20||Psalm 139:7-10|
|All-knowing||1 John 3:20||John 16:30; 21:17||1 Cor. 2:10-11|
|Sanctifies||1 Thess. 5:23||Heb. 2:11||1 Pet. 1:2|
|Life-giver||Gen. 2:7; John 5:21||John 1:3; 5:21||2 Cor. 3:6, 8|
|Fellowship||1 John 1:3||1 Cor. 1:9||2 Cor. 13:14; Phil. 2:1|
|Eternal||Psalm 90:2||Micah 5:1-2||Rom. 8:11; Heb. 9:14|
|A Will||Luke 22:42||Luke 22:42||1 Cor. 12:11|
|Speaks||Matt. 3:17; Luke 9:25||Luke 5:20; 7:48||Acts 8:29; 11:12; 13:2|
|Love||John 3:16||Eph. 5:25||Rom. 15:30|
|Searches the heart||Jer. 17:10||Rev. 2:23||1 Cor. 2:10|
|We belong to||John 17:9||John 17:6|
|Savior||1 Tim. 1:1; 2:3; 4:10||2 Tim. 1:10; Titus 1:4; 3:6|
|We serve||Matt. 4:10||Col. 3:24|
|Believe in||John 14:1||John 14:1|
|Gives joy||John 15:11||John 14:7|
|Judges||John 8:50||John 5:21, 30|