The call expressed in this song is found in such passages as Psalms 66, 95, 96, 98, 100 and 150.
The fulfillment of this vision is pictured in Revelation 7:9-17 and 19:1-8.
God’s children are called to and gathered to give worship to all three members of the Trinity. Belgic Confession, Article 8, gives the clearest explanation of the three persons of the Trinity, including not only their identity, but also their nature and tasks: “The Father is the cause, origin, and source of all things, visible and invisible. The Son is the Word, the Wisdom, and the image of the Father. The Holy Spirit is the eternal power and might, proceeding from the Father and the Son.”
Heidelberg Catechism, Lord’s Day 8, Questions and Answers 24 and 25 does so in much briefer form. As does the Belhar Confession, Section 1: “We believe in the triune God, Father, Son and Holy Spirit, who gathers, protects and cares for the church through Word and Spirit. This, God has done since the beginning of the world and will do to the end.”