The order of the priesthood is not something the New Testament church can afford to ignore or neglect. The Scriptures are clear that there is a royal priesthood, however the priesthood is for the chosen elect, not the called (1 Peter 2:8; Revelations 1:6; Revelations 5:10). The Gospels teach us that “many are called, but a few are chosen” (Matthew 22:14). The Scriptures could very well say, ‘many are called, but few are the priesthood.’ Peter spoke of a chosen (elect) race of priests. That was not for the whole church, just as it wasn’t for all of Israel. Moses wrote of God telling Israel that if they would keep the covenant, and obey His voice of truth, that they would be a kingdom of priests (Exodus 19:6). This was spoken to Israel as they arrived at Mt. Sinai. The call was made but only a few were chosen, the Levites. When Moses had broken the tablets because of the Israelite’s gross sin and idolatry, Moses called for those who would stand on the Lord’s side, and it is written that only the Levites, the priests, cleaved to the Lord (Exodus 32:26). This is especially important to understand, as we are being given the same choice being in the church, who will choose to be part of the priesthood?

As the priesthood was established through Moses, King David had established various orders when ushering in the ark into the tabernacle of David. Irenaeus explains in his work “Demonstration of Apostolic Teaching” that the Tabernacle of David pertains to the resurrection. It also pertains to bringing in the order of the priesthood that would usher in the Ark of the Covenant, the glory of God. David understood the gravity of bringing the glory out of correct order, “For because you did not do it the first time, the LORD our God broke out against us, because we did not consult Him about the proper order.” (1Chronicles 15:13). David learned at great cost the repercussions of not bringing in the glory of God through the order of the priesthood that God had ordained. When the glory of God comes at the end of the age, as was prophesied “For the earth will be filled with the knowledge of the glory of the LORD, As the waters cover the sea.” (Habakkuk 2:14), how can the church today speak on the glory, in such a careless way, and ignore the glaring fact that the priesthood the church is called to is not where it should be? The church claims to be part of the royal priesthood, but is ignorant of the type of sacrifices that are still required of us (Romans 12:1), and has little comprehension of the priestly order that is still in effect, although in a dormant state, due to the church departing from its former conduct.
The Apostle Paul instructed “Let all things be done decently and in order.” (1 Corinthians 14:40). Observe Ignatius’s writing regarding not understanding the weightiness of keeping God’s order, especially in the church today, and how this affects the church.

For if he that rises up against kings is justly held worthy of punishment, inasmuch as he dissolves public order, of how much sorer punishment, suppose ye, shall he be thought worthy, (Comp. Heb_10:29) who presumes to do anything without the bishop, thus both destroying the [Church’s] unity, and throwing its order into confusion? For the priesthood is the very highest point of all good things among men, against which whosoever is mad enough to strive, dishonors not man, but God, and Christ Jesus, the First-born, and the only High Priest, by nature, of the Father. Let all things therefore be done by you with good order in Christ. Let the laity be subject to the deacons; the deacons to the presbyters; the presbyters to the bishop; the bishop to Christ, even as He is to the Father. (1)
Ignatius specified a trait that is the cause and effect of destroying the church’s unity, by revealing that doing things out of order in the church will open a door to confusion. Notice that the offense is not even against the Bishop and the priesthood, it is against God himself. This may give clarity as to why there is so much division in just one denomination alone, not including all the numerous denominations that are separated from the original church.
The order of who is subject to whom, according to rank and order, is displayed plainly by Ignatius. In the Old Testament Joel’s army is known to “not break their ranks” (Joel 2:7). Can any of us think of a church that we came from that followed this order? Most churches are governed by pastors, some have a board of elders or deacons, and the like. As it is today, the roles of the Bishop, the Presbyter and the Deacon are not following the pattern of the priesthood as God intended. The Bishop fulfilled the role of the High priest in the church. The Presbyters were the rank of the Sanhedrin, the elders, and the Deacons were of the office of the prophet.

Being separated or not under this priestly order means one is not a part of the true church. The church is a body, and no one is just out on their own (1 Corinthians 12:12). If God intended for us as believers to be on our own, claiming ‘all I need is the Holy Spirit and Jesus Christ’, as some people do, then why would God establish a church with a priestly order and expect us to follow it? Why did the Apostles go through all the trouble and toil of establishing this order around the world, only for others to say ‘that’s not for me, all I need is the Lord.’ Irenaeus exposes the minds of those who separate themselves from the order that God has set in the church.
For this gift of God has been entrusted to the Church, as breath was to the first created man, for this purpose, that all the members receiving it may be vivified; and the [means of] communion with Christ has been distributed throughout it, that is, the Holy Spirit, the earnest of incorruption, the means of confirming our faith, and the ladder of ascent to God. “For in the Church,” it is said, “God hath set apostles, prophets, teachers,” (1Co 12:28) and all the other means through which the Spirit works; of which all those are not partakers who do not join themselves to the Church, but defraud themselves of life through their perverse opinions and infamous behavior. (2)
Apostles are the head of the church, not pastors, as Irenaeus echoes the order given by the Apostle Paul; thus unmasking that those of perverted opinions are the type who detach themselves from the apostles and prophets, and are disconnected from the church. If the church is not in order, like the church that was established two thousand years ago, how can it expect it to receive the glory of God? This is precisely why the Lord brings back the Spirit of Elijah at the end. To prepare the priesthood that has been lost, as prophesied in Malachi. To God be the glory, Amen.
References:
1. Ignatius-(Disciple of Apostle John)-Epistle to Smyrnaeans, Ch. IX Vol. 1
2. Irenaeus-Against Heresies Book 3 Ch. XXIV, Vol. 1