John the Apostle
Revelation 13:9BSB·traditional attribution

He who has an ear, let him hear:

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

If any man have an ear, let him hear. And diligently attend to this mystical description of antichrist, as being matter of some difficulty to understand, as well as of great moment and importance, and seriously consider it, that he may know him, and his followers, and avoid them; See Gill on Rev 1:7. .

Albert Barnes Presbyterian @notesbybarnes

Verse 9. If any man have an ear, let him hear. . The idea here is, that what was here said respecting the "beast" was worthy of special attention, as it pertained to most important events in the history of the church.