Death but a Change.
These heavenly personages talked, not to Jesus but with him, about His approaching death, and resurrection, one of the vital things in Christ's ministry which Peter could not comprehend. Surely after this glorious vision of two heavenly beings. Death would lose much if not all its terror for Peter, James, and John. They would know that even if wicked men did kill their Master, that He would still live and still be their Lord and Savior. Death, to them, after this, would be just a "departure." They would realize that "Death hath nothing terrible in it, but what life hath made so."
"It is Good to be Here."
Peter by inspiration had received assurances that Jesus was indeed the Christ; now he witnessed a visible sign of his testimony. Desiring to have a monument to this outward sign, something which other eyes beside his might behold, he cried, out of the impulsiveness of his heart, "Master, it is good for us to be here, and let us make three tabernacles; one for thee, and one for Moses, and one for Elias." But suddenly, as Moses and Elias "departed," a cloud overshadowed them and a voice came out of the cloud saying, "This is My beloved Son hear Him!"
Sources of Testimony.
Peter's testimony was, by this time, made strong and his faith proved:[[4]]
(1) By the confirmation of miracles; (2) By seeing heavenly beings; (3) By inspiration; (4) By hearing not only the testimony of these angels but the Divine testimony of God Himself!
Surely his faith is now built upon the Rock, and the gates of hell cannot prevail against it!
This is true; and henceforth, we may safely conclude as we follow his career, that not a shadow of doubt of the divinity of Christ's mission ever crosses Peter's mind.
When we think of Peter having been in almost daily contact with the Savior of men, we may conclude that his testimony grew very slowly, but if so, like the oak tree that grows slowly to, it was all the more enduring.