If a pastor has committed adultery (or divorced his wife), and he repents of his sin, can he return to a position leading a church (e.g., as a pastor or elder)?
The Bible is clear that a man in the church must meet strict tests of character to be eligible to serve as an elder or pastor in the body of Christ:
Titus 1:5 For this reason I left you in Crete, that you would set in order what remains and appoint elders in every city as I directed you,
Titus 1:6 namely, if any man is above reproach, the husband of one wife, having children who believe, not accused of dissipation or rebellion.
Titus 1:7 For the overseer must be above reproach as God’s steward, not self-willed, not quick-tempered, not addicted to wine, not pugnacious, not fond of sordid gain,
Titus 1:8 but hospitable, loving what is good, sensible, just, devout, self-controlled,
Titus 1:9 holding fast the faithful word which is in accordance with the teaching, so that he will be able both to exhort in sound doctrine and to refute those who contradict.
1Tim. 3:2 An overseer, then, must be above reproach, the husband of one wife, temperate, prudent, respectable, hospitable, able to teach,
1Tim. 3:3 not addicted to wine or pugnacious, but gentle, peaceable, free from the love of money.
1Tim. 3:4 He must be one who manages his own household well, keeping his children under control with all dignity
1Tim. 3:5 (but if a man does not know how to manage his own household, how will he take care of the church of God?),
1Tim. 3:6 and not a new convert, so that he will not become conceited and fall into the condemnation incurred by the devil.
Notice in both passages Paul requires that any man desiring to lead the church of God must be "beyond reproach" and faithful to his one (and only) wife, among other qualifications. If a man falls into a serious sin of the kind Paul lists, then he cannot be said to be beyond reproach. Likewise, if he commits adultery, then is not a "one woman man." Therefore, he is forever barred from church leadership according to scripture.
A pastor or elder who commits adultery or violates his marriage vows forfeits his opportunity to lead in the church, because he fails the character tests Paul gave to the church. These test were given to ensure the church had proper role models in leadership positions, whom the body of Christ could emulate.
Equally important, these character tests ensure the body is protected from the hypocrisy and missteps of men of weak character. Even if a pastor were to repent of his mistakes, his past sin would still limit his ability to serve as a role model to others, therefore he is barred from leadership to avoid confusing believers.
Notice in 1Tim 3:4-5 Paul says that when a man has shown evidence he cannot manage the affairs of his own household well (i.e., a simple task), then he is also demonstrating he is unqualified to manage the household of God (i.e., a more difficult task).
Finally, disqualification from leadership doesn't mean disqualification from participation in the body of Christ. A fallen pastor may still be forgiven by his brothers and sisters and restored to fellowship in the church body provided he repents of his sin. From that point, he can play an important and useful role in the body of Christ serving in a variety of capacities as a member of the congregation. Nevertheless, his repentance does not erase his past moral failings, and according to Paul he has rendered himself ineligible to hold future leadership positions.
Remember, leadership in the church is not a right; it is a privilege. Holding a position of leadership is contingent on a meeting strict tests of character, because we want every leader in the church to stand as an example to the church body of lifelong godliness and character.
