The teaching of the first century Christians can be found in the New Testament, specifically in the book of Acts. If a congregation claims to be Christian this must follow the scriptural pattern of appointing deacons.
The very first chapters speaks of the establishment of the church and later on as one reads, there can be found a pattern of how the church was organized. Part of this organization it links to the fact of having deacons.
Likewise must the deacons be grave, not doubletongued, not given to much wine, not greedy of filthy lucre; Holding the mystery of the faith in a pure conscience. And let these also first be proved; then let them use the office of a deacon, being found blameless. Even so must their wives be grave, not slanderers, sober, faithful in all things. Let the deacons be the husbands of one wife, ruling their children and their own houses well. For they that have used the office of a deacon well purchase to themselves a good degree, and great boldness in the faith which is in Christ Jesus. – 1 Timothy 3:8-13