Just like the rest of the scriptures, there is no mention of a Trinity in Jude.
Jude 1—“To those who have been called, who are loved in God the Father and kept for Christ Jesus” (NIV)
“God the Father” is obviously a completely separate and distinct person from “Christ Jesus”. If the Trinity doctrine were true, there should be a mention of the Holy Spirit at this point, but there isn’t.
Jude 4—“They are ungodly people, who pervert the grace of our God into a license for immorality and deny Jesus Christ our only Sovereign as Lord” (NIV)
Once again, “God” is shown to be someone other than Jesus Christ, and there is no mention of the Holy Spirit.
Jude 20,21—“By building yourselves up in your most holy faith and praying in the Holy Spirit, keep yourselves in God’s love as you wait for the mercy of our Lord Jesus Christ to bring you eternal life” (NIV)
The Holy Spirit is mentioned, but “praying in the Holy Spirit” indicates that it is not a person. This thought goes right over Trinitarians’ heads. “God” is again mentioned as someone who is not “our Lord Jesus Christ”.
Jude 25—“to the only God our Savior be glory, majesty, power and authority, through Jesus Christ our Lord” (NIV)
This doxology of the letter goes to “the only God our Savior . . . through Jesus Christ our Lord”, which shows that Jesus is a conduit to God (John 14:6), and not God himself.
Thus the letter of Jude provides powerful proof that Jesus Christ is not God, and that the Holy Spirit is not a person, so there cannot be any Triune God.