We; I, and James, and John. Heard: the apostle avoucheth himself to have been an ear-witness, as well as eye-witness, of Christ's glory, hereby intimating that there was as much certainty of the gospel, even in a human way, as could possibly be obtained of any thing that is done in the world, seeing men can be humanly certain of nothing more than of what they perceive by their senses: compare 1 John 1:1,3. The holy mount; so called, not because of any inherent holiness in it, but because of the extraordinary manifestation of God's presence there; in the same sense as the ground is called holy where God appeared to Moses and to Joshua, Exodus 3:5 Joshua 5:15.
Related Commentaries of 2 Peter 1:18
2 Peter 1:18
18 And this voice which came from heaven we heard, when we were with him in the holy mount.