John the Apostle
Revelation 17:8BSB·traditional attribution

The beast that you saw—it was, and now is no more, but is about to come up out of the Abyss and go to its destruction. And those who dwell on the earth whose names were not written in the Book of Life from the foundation of the world will marvel when they see the beast that was, and is not, and yet will be.

Matthew Henry Presbyterian @wholebiblehenry

Here we have the mystery of this vision explained. The apostle wonders at the sight of this woman: the angel undertakes to open this vision to him, it being the key of the former visions; and he tells the apostle what was meant by the beast on which the woman sat; but it is so explained as still to need further explanation. 1.

Commenting on Revelation 17:7-13

John Gill Reformed Baptist @doctorgill

The beast which thou sawest was, and is not,.... It is added at the end of the verse where the same description is given, "and yet is"; this beast is to be understood not of the devil, who "was" the god of this world, "is not", being cast out by Christ, and yet is in being; for he, the dragon, is distinguished from this beast...

Albert Barnes Presbyterian @notesbybarnes

Verse 8. The beast that thou sawest was, and is not. In the close of the verse it is added, "and yet is"--"the beast that was, and is not, and yet is." There are three things affirmed here: first, that there is a sense in which it might be said of the power here referred to that it "was," or that before this it had...