"Do your best to present yourself to God as one approved, a worker who has no need to be ashamed, rightly handling the word of truth".
2 Timothy 2:15
A minister who teaches the church MUST be equipped in sound systematic theology. Why? How else can he rightly divide the Word of God if he does not comprehend the unified system of truth, as presented in Holy Scripture? A minister has to preach the whole counsel of God and systematic theology provides the tools for such a man to do this. A man in the pulpit without training in systematic theology is like a plumber working on a boiler without a tool bag. It is that serious!
Many men who are allowed into pulpits with no theological training; but would you allow such a man to function as a primary school teacher, an electrician or a nurse to work without formal training? Of course not. So why do we place the bar so low at times for the minister serving in the church of God?
I have several book shelves with various authors presenting their systematic theologies. One that has remained a faithful friend to me over many years has been Louis Berkhof's Systematic Theology (in one volume). Furthermore this work comes in three sizes.
A Summary of Christian Doctrine: This is the slimmest of the three possibilities. It is published by the Banner of Truth and it provides a succinct summary of Christian truth.
Manual of Christian Doctrine: This is the medium size book and it is most useful to train a man who needs to be further equipped for Christian ministry at the early stages.
Systematic Theology (one Volume): This is the full work comprising some 738 pages without the index.
This work is highly reliable, doctrinally stable and it equips the church in what is known as the analogy of faith. We must interpret Scripture by Scripture. The Westminster Confession makes this plain in its first chapter, 1:9.
"The infallible rule of interpretation of Scripture is the Scripture itself: and therefore, when there is a question about the true and full sense of any Scripture (which is not manifold, but one), it must be searched and known by other places that speak more clearly".