It is truly amazing how our God works. His sovereignty is so complex, yet so simple. He rules, governs and dictates every atom of every galaxy with an iron fist, yet we are able to make decisions and choices at our own discretion, according to our nature. "Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutable his ways!" Romans 11.33
As we know, ministry is a sacred task. One that no minister should ever take lightly. From the minister of children to the minister of the elderly, all of God's work has equal value and importance. Thus, as ministers, we should make every human effort to maximize our ministry in a manner that is pleasing to God.
But the question must be raised. If God is sovereign, why must we work so hard to be "the sharpest tool in the shed" for the sake of Christ? Why must we strive for holiness and soundness of theology to be used of God in the growing of His kingdom? God is more than able to use even the most sinful christian to expand his kingdom isn't He?
The obvious answer is yes, God can and does use sinful men and women to expand His kingdom on a daily basis. I would argue that God uses "defeated" christians to give himself glory in the expansion of His kingdom. Even a fallen pastor can prove to bear fruit simply by someone witnessing the sincerity of his repentance.
To be sure, if your only striving for holiness and soundness of theology to be effective in ministry, you may want to re-evaluate your understanding of the atonement and your love for God.
Charles H Spurgeon in his work "Lectures to my students" anticipates questions like these and in my opinion gives great insight. He writes:
"...but we cannot regard God’s absolutely sovereign acts as a rule for our action. He may, in His own absoluteness, do as pleases Him best, but we must act as His plainer dispensations instruct us; and one of the facts which is clear enough is this, that the Lord usually adapts means to ends, from which the plain lesson is, that we shall be likely to accomplish most when we are in the best spiritual condition; or in other words, we shall usually do our Lord’s work best when our gifts and graces are in good order, and we shall do worst when they are most out of trim. This is a practical truth for our guidance. When the Lord makes exceptions, they do but prove the rule... It will be in vain for me to stock my library, or organise societies, or project schemes, if I neglect the culture of myself; for books, and agencies, and systems, are only remotely the instruments of my holy calling; my own spirit, soul, and body, are my nearest machinery for sacred service; my spiritual faculties, and my inner life, are my battle axe and weapons of war... It is not great talents God blesses so much as likeness to Jesus. A holy minister is an awful weapon in the hand of God.”
-Spurgeon, Charles H. (2010-05-04). Lectures to My Students (p.7-8). Zondervan. Kindle Edition.
This quote is full of truth!!!
Although God is sovereign, we must do our very best, as it regards human effort, in the building up of the spirit that God has quickened within us. We must strive for Christ-likeness if we are to be constantly effective weapons in the hands of God. And a truly Christ like weapon will preach the Word, for he/she knows that it is the Word, accompanied by the Spirit's unction, that brings about God’s will in our ministries.
“For as the rain and the snow come down from heaven and do not return there but water the earth, making it bring forth and sprout, giving seed to the sower and bread to the eater, so shall my word be that goes out from my mouth; it shall not return to me empty, but it shall accomplish that which I purpose, and shall succeed in the thing for which I sent it." Isaiah 55.10-11