John the Apostle
Revelation 6:2ESV·traditional attribution

And I looked, and behold, a white horse! And its rider had a bow, and a crown was given to him, and he came out conquering, and to conquer.

Matthew Henry Presbyterian @wholebiblehenry

Here, 1. Christ, the Lamb, opens the first seal; he now enters upon the great work of opening and accomplishing the purposes of God towards the church and the world. 2. One of the ministers of the church calls upon the apostle, with a voice like thunder, to come near, and observe what then appeared. 3. We have the vision itself, Rev 6:2.

Commenting on Revelation 6:1-2

John Gill Reformed Baptist @doctorgill

And I saw, and behold a white horse,.... Representing the ministration of the Gospel in the times of the apostles, which were just now finishing, John being the last of them, who saw this vision; and the "horse" being a swift, majestic, and warlike creature, and fearless of opposition and war, may design the swift progress of the Gospel in the world, the majesty, power...

Albert Barnes Presbyterian @notesbybarnes

Verse 2. And I saw, and behold. A question has arisen as to the mode of representation here: whether what John saw in these visions was a series of pictures, drawn on successive portions of the volume as one seal was broken after another; or whether the description of the horses and of the events was written on the volume, so that John read it...