Martin Luther and the Priesthood of All Believers

"Now we, who have been baptized, are all uniformly priests ... The only addition received by the priests is the office of preaching, and even this with our consent... Thus it says in 1 Peter 2, "Ye are an elect race, a royal priesthood, and a priestly kingdom." It follows that all of us who are Christian are also priests. Those whom we call priests are really ministers of the word and chosen by us; they fulfil their entire office in our name. The priesthood is simply the ministry of the word. So in 1 Corinthians 4 it says: "Let a man account of us as of ministers of Christ and stewards of the mysteries of God."
That being the case, it follows (i) that any one who has been called by the church to preach the Word, but does not preach it, is in no way a priest; and (ii) that the sacrament of ordination cannot be other than the rite by which the church chooses its preacher. That is how Malachi 2 defines a priest: "The priest's lips should keep knowledge, and they should seek the law at his mouth; for he is the messenger of the Lord of Hosts." ...
Therefore every one who knows that he is a Christian should be fully assured that all of us alike are priests, and that we all have the same authority in regard to the word and the sacraments, although no one has the right to administer them without the consent of the members of his church. ...
A joyful liberty would come back to us, in which we should understand that we are all equal by any law whatever; and, when the oppressive yoke had been cast aside, we should know that he who is a Christian possesses Christ; that he who possesses Christ possesses all things that are Christ's, and is able to do all things."

Martin Luther, Pagan Servitude of the Church (1520) part 6.