Biblical explanation
The Bible strongly teaches that there is one God. Deuteronomy 6:4 says, "Hear, O Israel: The LORD our God is one LORD." First Corinthians 8:4 likewise says, "there is none other God but one." At the same time, Scripture identifies the Father as God (1 Corinthians 8:6), the Son as God (John 1:1; John 20:28), and the Holy Spirit in divine terms (Acts 5:3-4). The Father, Son, and Holy Spirit are also distinguished from one another. At Jesus' baptism, the Son is baptized, the Spirit descends like a dove, and the Father's voice comes from heaven (Matthew 3:16-17). Jesus commanded baptism "in the name of the Father, and of the Son, and of the Holy Ghost" (Matthew 28:19). Second Corinthians 13:14 similarly places all three together: "The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost." Jesus also spoke of the Father sending another Comforter, the Holy Spirit (John 14:16-17,26). The Bible therefore presents three distinct divine persons while maintaining the truth that God is one. Scripture gives us the essential truths needed to understand God, but it does not provide a philosophical explanation of every aspect of God's eternal nature. The biblical emphasis is on who God is and how He has revealed Himself rather than on explaining every mystery concerning His existence.
Key takeaway
Salvation is entirely by grace through faith in Christ. His atoning sacrifice, heavenly ministry, and intercession are the foundation of assurance; obedience, Sabbath faithfulness, and loving service are the fruit of a redeemed life, never a way to purchase acceptance with God.