God expects Christians to behave certain ways, and warns us to not have anything to do with those who call themselves Christians but live sinfilled lives. Indeed, we are warned that folks who call themselves God’s people, but are not, are dangerous to those who are truly God’s people.
Leave the presence of a fool, or you will not discern words of knowledge.
He who goes about as a slanderer reveals secrets,
Therefore do not associate with a gossip.
15 “If your brother sins, go and show him his fault in private; if he listens to you, you have won your brother. 16 But if he does not listen to you, take one or two more with you, so that by the mouth of two or three witnesses every fact may be confirmed. 17 If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector.
1 Thessalonians 4:1-8
Finally then, brethren, we request and exhort you in the Lord Jesus, that as you received from us instruction as to how you ought to walk and please God (just as you actually do walk), that you excel still more. 2 For you know what commandments we gave you by the authority of the Lord Jesus. 3 For this is the will of God, your sanctification; that is, that you abstain from sexual immorality; 4 that each of you know how to possess his own vessel in sanctification and honor, 5 not in lustful passion, like the Gentiles who do not know God; 6 and that no man transgress and defraud his brother in the matter because the Lord is the avenger in all these things, just as we also told you before and solemnly warned you. 7 For God has not called us for the purpose of impurity, but in sanctification. 8 So, he who rejects this is not rejecting man but the God who gives His Holy Spirit to you.
1 Corinthians 5:11
But now I am writing to you that you must not associate with anyone who claims to be a brother or sister but is sexually immoral or greedy, an idolater or slanderer, a drunkard or swindler. Do not even eat with such people.
8 For you were once darkness, but now you are light in the Lord. Live as children of light 9 (for the fruit of the light consists in all goodness, righteousness and truth) 10 and find out what pleases the Lord. 11 Have nothing to do with the fruitless deeds of darkness, but rather expose them. 12 It is shameful even to mention what the disobedient do in secret.
9 But avoid foolish controversies and genealogies and arguments and quarrels about the law, because these are unprofitable and useless. 10 Warn a divisive person once, and then warn them a second time. After that, have nothing to do with them. 11 You may be sure that such people are warped and sinful; they are self-condemned.
1 Timothy 4:1-8
The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons. 2 Such teachings come through hypocritical liars, whose consciences have been seared as with a hot iron. 3 They forbid people to marry and order them to abstain from certain foods, which God created to be received with thanksgiving by those who believe and who know the truth. 4 For everything God created is good, and nothing is to be rejected if it is received with thanksgiving, 5 because it is consecrated by the word of God and prayer. 6 If you point these things out to the brothers and sisters, you will be a good minister of Christ Jesus, nourished on the truths of the faith and of the good teaching that you have followed. 7 Have nothing to do with godless myths and old wives’ tales; rather, train yourself to be godly. 8 For physical training is of some value, but godliness has value for all things, holding promise for both the present life and the life to come.
2 Timothy 2:15-17
15 Be diligent to present yourself approved to God as a workman who does not need to be ashamed, accurately handling the word of truth. 16 But avoid worldly and empty chatter, for it will lead to further ungodliness, 17 and their talk will spread like gangrene. Among them are Hymenaeus and Philetus,
2 Timothy 3:1-7
1 But mark this: There will be terrible times in the last days. 2 People will be lovers of themselves, lovers of money, boastful, proud, abusive, disobedient to their parents, ungrateful, unholy, 3 without love, unforgiving, slanderous, without self-control, brutal, not lovers of the good, 4 treacherous, rash, conceited, lovers of pleasure rather than lovers of God— 5 having a form of godliness but denying its power. Have nothing to do with such people. 6 They are the kind who worm their way into homes and gain control over gullible women, who are loaded down with sins and are swayed by all kinds of evil desires, 7 always learning but never able to come to a knowledge of the truth.