Peter here refers to the transfiguration of Christ on the mount (Matthew 17:1–5), which was a type of His second coming. Moses was a type of the resurrection saints, and Elijah of those who shall be translated without dying. Peter, James, and John were a type of the Jewish remnant who shall see Him when He comes, and the remaining disciples at the foot of the mount, unable to cast the demon out of the boy, of those professed followers of Jesus who shall be left behind at the rapture and shall be powerless to cast the demons out of the possessed people of that period.