Nowhere does it say that all elders are pastors.
The opening poster addressed this in a response, of course. Acts 20:28 and the opening verses of I Peter 5 tell elders to pastor.
I don't know that all who pastor are elders. But the elders of the church are to pastor.
Nowhere does it say that every one in the assembly is to have his turn to minister during the time they are gathered together.
Not exactly in those words. But take a look at I Corinthians 14. Paul presents all prophesying in a positive light when he mentions the idea of an unlearned or unbelieving man coming into the assembly. He says that when they come together 'every one of you' has a psalm, doctrine, tongue, revelation, interpretation. He says, 'let all things be done unto edifying.' So 'every one of you' is to be allowed to do these things in an edifying manner.
And he also addresses the Corinthians and all who believe in Jesus and says, "for ye may all prophesy, one by one...." So if the Spirit does move an individual to prophesy, he should be allowed to do so within the guidelines the Lord has given in the scripture.
What I don't see is any kind of indication that speaking in church was limited to elders. Romans 12 commands the one gifted to prophesy to prophesy, the one gifted to teach to teach, and the one gifted to exhort to exhort. I Peter 4 tells believers to minister their gifts to one another as good stewards of the manifold grace of God. Stewardship is a serious issue. The elders who pastor the flock of God should be encouraging stewardship of spiritual gifts, including teaching, prophesying, and edification.
Romans 12 commands the one gifted to teach to teach. It doesn't say that this is only the case for elders. Where else would they have used this gift except for the assembly, i.e, the 'church'? Paul instructed Titus that a bishop be 'apt to teach.' (Paul uses 'elders' and 'bishop' interchangeably in the passage. See also Acts 20:28 where the elders in one city church are called 'bishops' and I Peter 5 where elders are told to take 'oversight' of the flock of God.)
If those appointed bishops are to be 'apt to teach' before they are appointed bishops, wouldn't they have shown evidence of this beforehand? How would they have demonstrated this except by teaching the assembly?
I think this points out one of the weaknesses of the teaching of the Reformed tradition, the idea that ordained ministers are to be 'ministers of the word and sacrament.' That's okay, I guess, unless you start limiting the ministry of the word and sacrament to ordained ministers. The scripture does not teach such an idea.
We also owe the confusion over pastors and elders to the Reformed tradition and the weird way Presbyterians copied the model of Geneva Switzerland in the time of John Calvin. Torrence had an interesting article on this in a Scottish theological journal in the mid 1980s. I saw a copy of it in my stuff as I was sorting through it recently.
In Germanic languages, the word 'priest' or similar words were used to refer to Old Testament 'priests', but the word derived for the Greek word for church elder. Luther wrote of the 'priesthood of all believers'-- not referring to the eldership of all believers. So there was a lot of confusion over that word. The Reformed folks in Switzerland started calling their ordained ministers 'pastors' (or their equivalent for it) out of Ephesians 4:11. They wanted a Christian form of city government and saw models in Greek-speaking communities in the 300's in Syria and North Africa that referred to their community leaders as 'elders.' So they did that. Their city councilmen were 'elders.' Church and state were merged so these men were active in church and the Christian community. If I'm not mistaken, they were likely the ones who made the judgments to drive Anabaptists out of town and threaten to burn them, who burnt Servetus, and passed judgment on those who would name their children with names like Claud instead of Abraham.
Scottish Presbyterians copied Geneva and blew their model up into a state church. They ended up with extra-Biblical unordained elders, which turned into the modern non-pastoral board elder. Originally, both the Genevan Reformed folks and the Scottish Reformed folks knew their 'elders' weren't Biblical elders, using Biblical elder verses to refer to pastors. But the Presbyterians got confused after a couple of hundred years and started using 'elder' verses to refer to their lay elders.