Chapter 3 — Part I — Article I (Of God the Father)
Section 92. Q. Is the Holy Trinity mentioned in the Old Testament also? A. Yes; only not so clearly. For instance: By the Word of the Lord were the heavens made, and all the hosts of them by the Breath of his mouth. Psalm xxxiii. 6. Holy, Holy, Holy is the Lord of Hosts: the whole earth is full of his glory. Isaiah vi. 3.