New City CatechismSýnishorn

Question: How many persons are there in God?

Answer: There are three persons in the one true and living God: the Father, the Son, and the Holy Spirit. They are the same in substance, equal in power and glory.

Commentary: The…Trinity, Father, Son, and Holy Ghost, being one God, is…necessary to us to be believed, not only as to the eternal…but especially for the knowledge of God's three great sorts of works on man: that is, as our Creator, and the God of nature; as our Redeemer, and the God of governing and reconciling grace, and as our Sanctifier, and the Applier and Perfecter of all to fit us to glory.

The Scripture tells us that there are three, and yet but one God.… We are to be baptised into the name of the Father, Son, and Holy Ghost (Matt. xxviii. 29.) And there are three that bear record in heaven, the Father, the Word, and the Holy Spirit, and these three are one (1 John v. 7.)… [That] God is one infinite, undivided Spirit; and yet that he is Father, Son, and Holy Ghost, must be believed. We must…know, believe and esteem him to be the only infinite, eternal, self-sufficient Spirit, vital Power, Understanding, and Will, our most perfect Life, Light, and Love; Father, Son, and Holy Ghost, of whom, and through whom, and to whom, are all things; our absolute Owner, Ruler, and Father; our Maker, our Redeemer, and Sanctifier.