Why is it said in the Creed that the Holy Spirit “spoke by the prophets?”
The statement “who spoke through the prophets” is said against certain heretics (the Marcionites and various gnostics), who taught that the books of the Old Testament were not written by the Holy Spirit, the Creed thereby confessing that the God of the Old Covenant and of the New is one, and his Spirit one. As the Apostle Peter writes: “No prophecy ever came by human will: holy men of God spoke, being moved by the Holy Spirit” (2Pe 1:21; see Q019, Q025).
The Apostles also spoke by the Holy Spirit: as the same Apostle Peter writes:
It was revealed to the prophets that not to themselves, but to us, they were ministering the things which have now been announced to you by those who preached the Gospel to you by the Holy Spirit sent down from heaven. (1Pe 1:12)
