All 3 Persons of the Godhead existed from the days of eternity; all 3 were active in Genesis 1 and the creation; all 3 were pictured in the Old Testament, see Isaiah 48:16; all 3 were present at the baptism of Jesus; all 3 are depicted in Acts 2; all 3 are important in the Great Commission baptism; and the 3 are represented in the inspired New Testament Letters such as by Paul:
“May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with all of you.” 2 Cor. 13:14; cf Philippans 2:1.
If you deny the Holy Spirit, you deny God. If you deny and ignore Jesus Christ, you deny God. All 3 continue working and must not be denied.