Salvation is historical. The OT view of salvation as effected through historic, divine intervention is fully honoured in the NT. As against Gnosticism, man is not saved by wisdom; as against Judaism, man is not saved by moral and religious merit; as against the Hellenistic mystery cults, man is not saved by a technique of religious practice; as against Rome, salvation is not to be equated with political order or liberty.
Man is saved by God’s action in history in the person of Jesus Christ (Rom. 4:25; 5:10; 2 Cor. 4:10f.; Phil. 2:6f.; 1 Tim. 1:15; 1 Jn. 4:9-10, 14). While the birth, life and ministry of Jesus are very unimportant, the stress falls upon his death and resurrection (1 Cor. 15:5f.); we are saved by the blood of his cross (Acts 20:28; Rom. 3:25; 5:9; Eph. 1:7; Col. 1:20; Heb. 9:12; 12:24; 13:12; 1 Jn. 1:7; Rev. 1:5; 5:9). As this message is proclaimed and men hear and come to respond in faith God’s salvation is brought to them (Rom. 10:8, 14f.; 1 Cor. 1:18-25; 15:1 I; 1 Thes. 1:4f.).
The specifically covenantal language employed in Acts 20:28 (peripoieomai, “to acquire”; cf. Ex 19:5; Is 43:21) and Acts 20:32; 26:18 (hagiazō, “to sanctify”; cf. Deut 33:3) reminds us of Luke’s record of Jesus’ last meal with his disciples, wherein he grounds the “new covenant” in his own death (Lk 22:19–20).
Scripture teaches three persons in one God (e.g. monotheism) in perfect unity sharing the same essence yet fulfilling different roles.
All persons of God are equal in essence, but they do not have the same roles. It is a heresy (called subordinationism) to affirm that there is an ontological subordination of one member of the Trinity to another, since they are identical in essence; nonetheless, it is clear that there is a functional subordination; that is, not only does each member have a different function or role, but some functions are also subordinate to others. Very briefly:
The Function of God the Father:
By His very title of "Father" and His label of "the first person of the Trinity," it is manifest that His function is superior to that of the Son and the Holy Spirit. The Father, for example, is presented as the Source, Sender, and Planner of salvation.
The Function of the God the Son:
The Son, on the other hand, is the Means, Sent One, and Achiever of salvation. The Father sent, and the Son came to save us; the Father planned it, but the Son accomplished it on the cross. This is why it is a heresy (called patripassianism) to claim that the Father suffered on the cross. only the son suffered and died. Further, the Son is eternally "begotten" or "generated" from the Father, but the Father is never said to be "begotten" or "generated."
The Function of God the Holy Spirit:
According to orthodox theology, both East and West, the Holy Spirit is said to "proceed" from the Father, but the Father never proceeds from the Holy Spirit-that is, the Father sends the Spirit, but the Spirit never sends the Father. In addition, however, according to orthodox Western theology, the Holy Spirit proceeds both from the Father and the Son (see John 15:26) a point of difference between East and West.
The point of all this is that the Father is the Planner, the Son is the Accomplisher, and the Holy Spirit is the Applier of salvation to believers. You can say it like this, the Father is the Source, the Son is the Means, and the Holy Spirit is the Effector of salvation-it is He who convicts, convinces, and converts.
We see that God is in perfect unity and oneness with three persons fulfilling different roles.
Debate Topic: Is the Trinity Doctrine Biblical? | Christian Apologetics and Research Ministry
"The Father, Son, and Holy Spirit are the three persons in the Godhead. Each are called God; each indwells the believer; each have wills; each speaks; each says you, yours, me, mine; each are self aware; and each are aware of others. The Father and Son relationship existed before creation and is still in existence now. We have the demonstration of the attributes of personhood and the manifestation of the inter-Trinitarian relationship of Father and Son. This relationship has not changed and will not change because God does not change, as Mal. 3:6 clearly teaches us. God is a Trinity, the Father, the Son, and the Holy Spirit. This is the true and living God."