John the Apostle
Revelation 13:5ESV·traditional attribution

And the beast was given a mouth uttering haughty and blasphemous words, and it was allowed to exercise authority for forty-two months.

Matthew Henry Presbyterian @wholebiblehenry

We have here an account of the rise, figure, and progress of the first beast; and observe, 1. From what situation the apostle saw this monster. He seemed to himself to stand upon the sea-shore, though it is probable he was still in a rapture; but he took himself to be in the island Patmos, but whether in the body or out of the body he could not tell. 2.

Commenting on Revelation 13:1-10

John Gill Reformed Baptist @doctorgill

And there was given unto him a mouth,.... The beast is said to have a mouth before, like the mouth of a lion, Rev 13:2; but now he was moved and stirred up by the dragon, the devil, to open it, not only in a cruel and voracious way, but in a haughty, lying, and blasphemous manner: and this was given him, it was at...

Albert Barnes Presbyterian @notesbybarnes

Verse 5. And there was given unto him a mouth speaking great things. John does not say by whom this was given; but we may suppose that it was by the "dragon," who is said () to have given him his power, and seat, and authority.