One of the earliest (non-canonical) letters that we have from the early Church is that of First Clement. This letter was written in A.D. 96 to deal with the strife that existed between the church in Rome and the church in Corinth. Clement was the leader of the church in Rome, and some Roman Catholic polemics suggest he was the fourth pope. (He could well have been Peter’s successor as the leader of this flock, which of course does not, in and of itself, prove the doctrine of the papacy. He appears to have been ordained by Peter as best we can tell.) Certain presbyters (ministers/elders) had been deposed in Corinth and Clement urges that they be restored. (It is interesting to note that Paul’s appeals to the Corinthian church had not brought about the peace and unity he so desired for that people.)
Clement’s letter is an appeal to restore due order in all things and to reinstate and obey their proper leaders. This Letter of Clement was so highly valued that it was read publicly in the church at Corinth until around A. D. 170. In this letter Clement refers to the presbyters "offering the gifts," by which he means celebrating the Eucharist. Other important insights are given in 1 Clement regarding the state of the ministry at this date. It is an immensely valuable document, though it was left out of the Canon, proving I think that apostolicity was directly linked with the makeup of the Canon.
I was reading 1 Clement a few days ago and noted these parts of the letter (sections 15-21):
Therefore let us unite with those who devoutly practice peace, and not with those who hypocritically wish for peace. For somewhere he says, "The people honors me with their lips, but their heart is far from me" and again "They blessed with their mouth but cursed with their heart" . . . For Christ is with those who are humble, not with those who exalt themselves over his flock. The majestic scepter of God, our Lord Jesus Christ, did not come with the pomp of arrogance or pride [though he could have done so], but in humility, just as the Holy Spirit spoke concerning him. . . . Accordingly, the humility and subordination of so many and such great men of renown have, through their obedience, improved not only us but also the generations before us, and likewise, those who have received his oracles in fear and truth. . . . Take care, dear friends, lest his many benefits turn into a judgment upon us all, as will happen if we fail to live worthily of him, and to do harmoniously those things which are good and well-pleasing in his sight.
You can sure get the sense, from these words, that how we treat others is at the core of Christian faith and that if we fail to live as we should, in view of who Christ is, judgment will surely fall upon us. Relationships and submission to church authority were immensely important to Clement.
"If it is possible, as far as it depends upon you, live at peace with everyone. Do not take revenge, my dear friends" (Romans 12:18-19a).