John the Apostle
Revelation 5:2BSB·traditional attribution

And I saw a mighty angel proclaiming in a loud voice, “Who is worthy to break the seals and open the scroll?”

Matthew Henry Presbyterian @wholebiblehenry

Hitherto the apostle had seen only the great God, the governor of all things, now, I. He is favoured with a sight of the model and methods of his government, as they are all written down in a book which he holds in his hand; and this we are now to consider as shut up and sealed in the hand of God. Observe, 1.

Commenting on Revelation 5:1-5

John Gill Reformed Baptist @doctorgill

And I saw a strong angel proclaiming with a loud voice,.... This was not the uncreated angel, Jesus Christ; for he is after spoken of as the lion of the tribe of Judah, and as the Lamb in the midst of the throne, but a created one; though who he was, whether Gabriel, as some say, because his name signifies the strong or mighty One...

Albert Barnes Presbyterian @notesbybarnes

Verse 2. And I saw a strong angel. An angel endowed with great strength, as if such strength was necessary to enable him to give utterance to the loud voice of the inquiry. "Homer represents his heralds as powerful, robust men, in order consistently to attribute to them deep-toned and powerful voices."--Professor Stuart.