If you are looking for a short book to explain the role of a pastor to a congregation or elder board and how the congregation can make best use of their pastors and elders, may I suggest this brief treatment by Robert Murray McCheyne.
A timeless exposition of 2 Timothy 4:1-2, a charge to both pastor and congregation with enough scriptural references and allusions to make for a good small group study. Book is formatted for easy reading and notation and includes many historical footnotes to bring the work thoroughly up to date.
It is available on Amazon in both kindle and paperback formats.
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