The gospel is inherently Trinitarian. Joel Beeke shows how one aspect of the gospel, spiritual adoption, is an act of Trinitarian cooperation:

The puritans emphasize that all the members of the Trinity are involved in our adoption. Stephen Marshall summarizes it this way: adoption is the gracious act of God the Father whereby he chooses us, calls us to himself, and gives us the privileges and blessings of being his children. God the Son earned those blessings for us through his propitiatory death and sacrifice, by which we become children of God (1 John 4:10), and applies them to us as Elder Brother. And the Holy Spirit changes us from children of wrath, which we are by nature, into children of God by means of regeneration; unites us to Christ; works in us a “suitable disposition” towards God and Christ; and seals our sonship as the Spirit of adoption, witnessing with our spirits that we are the sons of God. In that witnessing, the Spirit shows us God’s work of grace in our hearts and lives, and also “carries our hearts to God, and testifies to the Soul that God is [our] Father.”

—Joel R. Beeke, Heirs with Christ: The Puritans on Adoption (Reformation Heritage, 2008), 45–46.