Tampering with priesthood is a serious matter (Numbers 3:10, 38; 16:10, 32; 18:7; 2 Chronicles 26:18). Hebrews reaffirms this strict principle: “No one takes this honor [of priesthood] for himself, but only when called by God, just as Aaron was” (Hebrews 5:4). Jesus Himself could not be an Aaronic priest since He was a descendent of Judah (Hebrews 7:14). “Now if He [Christ] were on earth, He would not be a priest at all” (Hebrews 8:4). Even Roman Catholic reference works agree, church leaders were never called priests in New Testament times or among the Apostolic Fathers.
How, then, could a special priesthood arise? The answer is, very gradually, as power to make changes grew, and the Bible’s teaching became less known.
Over time, Roman Catholicism developed three authorities: 1. “The Magisterium” meaning the Pope and Bishops, with their Councils, 2. “The Scriptures” and, 3. “Traditions” that gained official endorsement. Multiple authorities led to a long history of departures from New Testament Christianity.
Many departures involved forms of worship. Though new in Christian settings, these forms tended to be old, adapted from ancient pagan practices (to attract pagans) or borrowed from Moses’ covenant (which Hebrews 8:13 calls “obsolete”). They were designed to appeal to the fleshly senses. Eventually, these forms came to include the burning of candles and incense, the use of holy water, beads, altars, images, instrumental music, and confessionals. Relics, crucifixes, and the sign of the cross supposedly warded off evil spirits. People were impressed by elaborate ceremonies, holy vestments, and grand buildings called cathedrals—all so foreign to the spirit and simplicity of New Covenant worship.
Though the Bible plainly states that Christ died “once for all” (Hebrews 10:10), priests claimed to sacrifice Christ at very mass, turning the bread into His literal flesh and the wine into His literal blood. For many centuries, church law denied the cup to laity (lest they spill Jesus’ blood) and required services to use holy Latin (even when few understood it). Though Jesus is the “one mediator between God and men” (1 Timothy 2:5), new doctrines made Mary, mother of Jesus, into a mediator, with favorite “saints” playing similar roles.