John the Apostle
Revelation 10:2BSB·traditional attribution

He held in his hand a small scroll, which lay open. He placed his right foot on the sea and his left foot on the land.

Matthew Henry Presbyterian @wholebiblehenry

Here we have an account of another vision the apostle was favoured with, between the sounding of the sixth trumpet and that of the seventh. And we observe, I. The person who was principally concerned in communicating this discovery to John - an angel from heaven, another mighty angel, who is so set forth as would induce one to think it could be no other...

Commenting on Revelation 10:1-7

John Gill Reformed Baptist @doctorgill

And he had in his hand a little book open,.... By which is meant not the Bible, the Scriptures of the Old and New Testament; or the book of the Gospel, the substance of which lies in a little room, and is no other than the preaching of Christ, and him crucified, as God's way of salvation; and which is now more open and manifest...

Albert Barnes Presbyterian @notesbybarnes

Verse 2. And he had in his hand a little book open. This is the first thing that indicated the purpose of his appearing, or that would give any distinct indication of the design of his coming from heaven. The general aspect of the angel, indeed, as represented in the former verse, was that of benignity, and his purpose, as there indicated, was light and peace.