Who will possibly stay in a relationship with a girlfriend or boyfriend "until death us do part" unless there is a deep devotion to that one person above all others, a commitment that is based on comprehensive knowledge and respect? That is the essence of marriage, leaving all others and cleaving to one until God shall separate by death.
Who will stay in the Christian ministry for one's entire working life unless one loves this work above all others, being unable to do anything else than preach the gospel and pastor the people of God to whom he preaches week by week? The Apostle Paul writes about a man who "sets his heart" on this work (1 Tim. 3:1). He is stretching out to make this his life's supreme calling. He is not talking about selfish ambition for prestige and power but for the high privilege of caring for the people whom the Son of God loved and for whom He suffered the death of the cross. So the first qualification for a lifetime's commitment to pastoral ministry is a strong inner desire. Our life is offered to God in building up His people and going after the lost until they all, with you, attain the stature of the fullness of Christ.
Clearly, this inward longing must be educated and informed. There must be an understanding of the New Testament requirements of the work of the pastor-preacher, and there is nowhere better to discover this in the Scriptures than the life of the Apostle Paul. There are some aspects to his calling that are peculiarly those of an Apostle, but the vast portion of the life of Paul—his defense of the faith, his setting forth of the full gospel of grace, his righteous character, his tireless zeal, his wisdom in handling tensions within a congregation—cannot be equalled as an example of a model minister. Once you have understood that your work is primarily focused on serving the Lord, then you will want to know where you can best appreciate what that requires. The New Testament will help you, especially the life of Paul. You will often ask, "Who is sufficient for this work?" and it is essential you ask that or the pride of office and its powers, as well as the gifts you have, will destroy you.
Let the inward longing also be validated by the godliest men you can meet, righteous, loving men, whose first love is the kingdom of God and its King, and who want to know of the credibility of your conversion, your understanding of the work of the ministry, your confessional faithfulness, your moral integrity, your emotional maturity, and your compassionate heart. They will want to probe you to ensure you do not have "funny ideas," and they can tell you "No," "Yes," or "Wait a while."
After this, the great army of ministers, pastors, and evangelists who have marched through the last two thousand years of the church's history will also supply you with hundreds of examples of the preacher's vocation. The church fathers, the Reformers, the Puritans, and many others will all overwhelm you as ministerial role models.
Along with those who have come before, there are today's role models. In many ways, they are the best, especially those men you meet who, in God's providence, are your contemporaries. They are a little older or younger than you but they seem to be giants. They have been Christians for many years; they have sat under rich biblical preaching; they have read widely; and they have developed wise opinions concerning the meaning of key passages, texts, and doctrines of the Bible. You will thank God for bringing them into your life. Friendship with them at seminary endures from ordination throughout the different pilgrimages God plans for you. Not a week goes by without you speaking on the phone and emailing one another. You share pastoral problems, management strategies, recent books, attendance at conferences, and the blessings and buffetings of ministerial life. When the call to a new sphere comes to you, they are the ones, after your wife, whose counsels and prayers you most covet. The ministry is no place for loners or friendless men.
If you are blessed to have a preacher as your example, the danger is obvious: you may choose to imitate those aspects of his gifts that you can most easily replicate. It is a very great danger. For example, you may consider his lack of household visitation because of his center-city parish as rationale for your neglect of this indispensable pastoral task. It is essential that you have more than one pastoral role model. The more pastors you know, the easier it will be to conduct a well-rounded ministry.
Most of all, it is the Lord who makes men fishers of men. There have been men whose gifts were limited but whose dependence on the Lord was heartfelt. Some of them, like David Brainerd, suffered with melancholy, yet they were made fishers of men. With little knowledge of church history, with few friends or a spiritual congregation to support them, they have gone as Joseph did, armed with God's Word, into the heart of their own Egypts, kingdoms of darkness. By casting themselves upon God, they overcame powerful temptations of the flesh and the loneliness of prison life without the friendly voice of another Christian, and there they subdued mighty kingdoms, obtained the promises of God to build His church, and wrought works of righteousness that we look back to today from our luxurious lifestyles as we humbly marvel and berate our self-pity.