Is it not wrong to ask a man that is not too faithful in attendance to take part in things like leading prayer etc. Also the Bible says to mark the people that are doing things like living in adultery etc. Why does the church not practice disfellowship?
This question is more of a judgment question than a Bible question. Certainly some principles can be suggested; however, there is not enough information to give a specific judgment. For instance, how unfaithful is “not too faithful.” Who is making the judgment? If “unfaithful” is based on worship attendance, what is the reason for absence? In general, if an individual is willfully absenting himself from worship on a regular and frequent basis, he is not one, who in the judgment of many, should be given a leading role in worship. Some congregations assign such duties in the hope that one will become more faithful. Worship leadership should not be used for that purpose. Such a practice is akin to making a person a deacon or elder in hope that he will become more actively engaged in the work of the congregation.
As to the second part of the question there is no good answer nor is there a uniform answer. The most often used excuse for not practicing withdrawal of fellowship is that it is not necessary because most people to whom it would apply have already withdrawn themselves before the congregation gets around to withdrawing. While that may be the case, it is still a non-compliance with the Biblical command to withdraw from those who walk disorderly. It is more likely that the truth is that fellowship has no meaning to many folks; thus withdrawing fellowship has no meaning or impact. Moreover, in large congregations there is often a lack of information about the members. A few members of the congregation may be aware of misconduct, but the elders are unaware and the members who know do not tell them. In large congregations, the elders may not even know many of the members, much less have an awareness of their conduct. In those instances, as the Webmaster of this site recently said in the class on 1 Corinthians 5 (available on this website in the lessons on 1 Corinthians), withdrawal is not effective when you have to introduce yourself before you withdraw.
You Must Hear the Gospel
Romans 10:17
You must hear the gospel and then understand and recognize that you are lost without Jesus Christ no matter who you are and no matter what your background is. The Bible tells us that “all have sinned, and come short of the glory of God.” (Romans 3:23) Before you can be saved, you must understand that you are lost and that the only way to be saved is by obedience to the gospel of Jesus Christ. (2 Thessalonians 1:8) Jesus said, “I am the way, the truth, and the life: no man cometh unto the Father, but by me.” (John 14:6) “Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.” (Acts 4:12) "So then faith cometh by hearing, and hearing by the word of God." (Romans 10:17)
You Must Believe
Hebrews 11:6
You must believe and have faith in God because “without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.” (Hebrews 11:6) But neither belief alone nor faith alone is sufficient to save. (James 2:19; James 2:24; Matthew 7:21)
You Must Repent
Acts 3:19
You must repent of your sins. (Acts 3:19) But repentance alone is not enough. The so-called “Sinner’s Prayer” that you hear so much about today from denominational preachers does not appear anywhere in the Bible. Indeed, nowhere in the Bible was anyone ever told to pray the “Sinner’s Prayer” to be saved. By contrast, there are numerous examples showing that prayer alone does not save. Saul, for example, prayed following his meeting with Jesus on the road to Damascus (Acts 9:11), but Saul was still in his sins when Ananias met him three days later (Acts 22:16). Cornelius prayed to God always, and yet there was something else he needed to do to be saved (Acts 10:2, 6, 33, 48). If prayer alone did not save Saul or Cornelius, prayer alone will not save you. You must obey the gospel. (2 Thess. 1:8)
You Must Confess
Romans 10:9
You must confess that Jesus Christ is the Son of God. (Romans 10:9-10) Note that you do NOT need to make Jesus “Lord of your life.” Why? Because Jesus is already Lord of your life whether or not you have obeyed his gospel. Indeed, we obey him, not to make him Lord, but because he already is Lord. (Acts 2:36) Also, no one in the Bible was ever told to just “accept Jesus as your personal savior.” We must confess that Jesus is the Son of God, but, as with faith and repentance, confession alone does not save. (Matthew 7:21)
You Must Be Baptized
Acts 2:38
Having believed, repented, and confessed that Jesus is the Son of God, you must be baptized for the remission of your sins. (Acts 2:38) It is at this point (and not before) that your sins are forgiven. (Acts 22:16) It is impossible to proclaim the gospel of Jesus Christ without teaching the absolute necessity of baptism for salvation. (Acts 8:35-36; Romans 6:3-4; 1 Peter 3:21) Anyone who responds to the question in Acts 2:37 with an answer that contradicts Acts 2:38 is NOT proclaiming the gospel of Jesus Christ!
You Must Be Faithful Unto Death
Revelation 2:10
Once you are saved, God adds you to his church and writes your name in the Book of Life. (Acts 2:47; Philippians 4:3) To continue in God’s grace, you must continue to serve God faithfully until death. Unless they remain faithful, those who are in God’s grace will fall from grace, and those whose names are in the Book of Life will have their names blotted out of that book. (Revelation 2:10; Revelation 3:5; Galatians 5:4)