Daniel 10

Daniel 10:11

I indeed maintain that even Gabriel in no other way foretells events to come than by the foreknowledge of the Spirit, by reason of the fact that one of the boons distributed by the Spirit is prophecy. And whence did he who was ordained to announce the mysteries of the vision to the man of desires derive the wisdom whereby he was enabled to teach hidden things, if not from the Holy Spirit? The revelation of mysteries is indeed the peculiar function of the Spirit, as it is written, "God has revealed them to us by his Spirit." — ON THE HOLY SPIRIT 16:38