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.

John Yoder on the Priesthood of all believers in the New Testament

"The work of Christ is described in Hebrews as the abolition of the priesthood. The perfect high priest, fully obedient among His brethren, by sacrificing Himself, puts an end to the recurrent functions of all priesthood, and gives us all access into the holy place. Priesthood, to the extent that it applies at all in the new covenant, is the character of the entire people of God, not of any single priestly person in the church. Thus Revelation 5 and 1 Peter 2 take up the mosaic phrase "a kingdom of priests" to designate the abolition of the distinct priestly role (whereas the prophetic role and the eldership, and something like the rabbinate, are carried over in the N.T. church). Priests joining the Jerusalem church did not create a Christian priesthood....
The conclusion is inescapable that the multiplicity of ministries is not a mere adiaphoron, a happenstance of only superficial significance, but a specific work of grace and a standard for the church ... We would expect, in a turbulent first-generation movement, that wisdom should call everyone to restrain his individualism; but the apostolic call is to each to be the most uniquely oneself. Not only should one not despise the other, not only should all work in unity like the organs of a healthy body, but each is invited to sharpen his or her distinctiveness (1 Pet. 4:10, Rom. 12:3, 6 ff). Harmony and diversity are not in tension but complementary."

John Howard Yoder, The Fullness of Christ: Paul's Vision of Universal Ministry (1987) 16-17