J. Vernon McGee:
The people of Israel were told clearly what kind of relationship they were to have with the sinful nations around them and among them. They had not driven those nations out of the promised land as they had been commanded. And yet God told them that they could still do that. He told them about all the evil that those nations would cause them. They chose to mingle with those other nations. In choosing that, they also chose to mingle with snares, traps, scourges and thorns in their eyes until their death. God*s warnings were unheeded by most of them and the results He predicted came upon them. They forfeited the influence they might have had on those other nations and suffered from the influence of the other nations.
Joshua 23:10: One man of you shall chase a thousand: for the LORD your God, he it is that fighteth for you, as he hath promised you. 11 Take good heed therefore unto yourselves, that ye love the LORD your God. 12 Else if ye do in any wise go back, and cleave unto the remnant of these nations, even these that remain among you, and shall make marriages with them, and go in unto them, and they to you: 13 Know for a certainty that the LORD your God will no more drive out any of these nations from before you; but they shall be snares and traps unto you, and scourges in your sides, and thorns in your eyes, until ye perish from off this good land which the LORD your God hath given you.
Much like the people of Israel, Christians are commanded to separate themselves from the unbelievers around them and from their sin. We are to share the gospel with them for in so doing we will overcome their evil and some of them will become Christians. Before we became Christians we were overcome with evil. God wants us to reverse the process and He will help us do it. If we foolishly mingle with them in their sin, God will not give us better results than the Israelites.
2 Corinthians 6:14: Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? 15 And what concord hath Christ with Belial? or what part hath he that believeth with an infidel? 16 And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people. 17 Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you, 18 And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty.
Romans 12:21: Be not overcome of evil, but overcome evil with good.
Mark 16:15: And he said unto them, Go ye into all the world, and preach the gospel to every creature.
Matthew 5:16: Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
Both the Israelites in their time and Christians in their time, are not only to separate themselves from evil but to associate themselves with God. Neither the Israelites nor Christians have ever won over unbelievers by joining with them in their sin.
Psalms 1:1-3: Blessed is the man that walketh not in the counsel of the ungodly, nor standeth in the way of sinners, nor sitteth in the seat of the scornful. But his delight is in the law of the Lord; and in his law doth he meditate day and night. And he shall be like a tree planted by the rivers of water, that bringeth forth his fruit in his season; his leaf also shall not wither; and whatsoever he doeth shall prosper.
Psalms 26:4-5: I have not sat with vain persons, neither will I go in with dissemblers. I have hated the congregation of evildoers; and will not sit with the wicked.
Proverbs 1:10: My son, if sinners entice thee, consent thou not.
Proverbs 2:10-15: When wisdom entereth into thine heart, and knowledge is pleasant unto thy soul; Discretion shall preserve thee, understanding shall keep thee: To deliver thee from the way of the evil man, from the man that speaketh froward things; Who leave the paths of uprightness, to walk in the ways of darkness; Who rejoice to do evil, and delight in the frowardness of the wicked; Whose ways are crooked, and they froward in their paths:
Proverbs 4:11-18: I have taught thee in the way of wisdom; I have led thee in right paths. When thou goest, thy steps shall not be straitened; and when thou runnest, thou shalt not stumble. Take fast hold of instruction; let her not go: keep her; for she is thy life. Enter not into the path of the wicked, and go not in the way of evil men. Avoid it, pass not by it, turn from it, and pass away. For they sleep not, except they have done mischief; and their sleep is taken away, unless they cause some to fall. For they eat the bread of wickedness, and drink the wine of violence. But the path of the just is as the shining light, that shineth more and more unto the perfect day.
Proverbs 12:11: He that tilleth his land shall be satisfied with bread: but he that followeth vain persons is void of understanding.
Proverbs 13:20: He that walketh with wise men shall be wise: but a companion of fools shall be destroyed.
Proverbs 14:7: The lips of the wise disperse knowledge: but the heart of the foolish doeth not so.
Proverbs 29:24: Whoso is partner with a thief hateth his own soul: he heareth cursing, and bewrayeth it not.
1 Corinthians 5:9-11: I wrote unto you in an epistle not to keep company with fornicators: Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world. But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolater, or a railer, or a drunkard, or an extortioner; with such an one no not to eat.
I Corinthians 15:33: Be not deceived: evil communications corrupt good manners.
2 Thessalonians 3:14-15: And if any man obey not our word by this epistle, note that man, and have no company with him, that he may be ashamed. Yet count him not as an enemy, but admonish him as a brother.