Why do Priests vest so elaborately when going to say Mass?

The Catholic Answers

In Exodus, XXVIII., 2-3, we read of God’s prescriptions of the vestments befitting the dignity of His religion. “Thou shalt make a holy vesture for Aaron thy brother; for glory and for beauty. And thou shalt speak to all the wise of heart, whom I have filled with the spirit of wisdom: that they may make Aaron’s vestments, in which he being consecrated may minister to me. And these shall be the vestments that they shall make.” Throughout the rest of the chapter God deigns to give the most minute directions as to the various vestments Aaron was to use. Not for a moment would Christ have condemned the principle of vestments after such a sanction by the infinitely wise God. He would be contradicting Himself. There can be nothing wrong with vestments in principle.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty