Be Separate; Obey and Be Blessed
Israel is not to intermarry with the peoples of Canaan, because, as God tells them, "they will turn your sons away from following Me, to serve other gods" (verse 4). Regrettably, the Israelites will not obey this command, and the history of Israel and Judah will reveal the bad results. Indeed, we may think of individual examples in the Old Testament like Solomon, whose many foreign wives induced him to forsake the living God, or the influence of the pagan Queen Jezebel on King Ahab. Yet, even for us today, God says basically the same thing (compare 2 Corinthians 6:14-18 2 Corinthians 6:14-18  Be you not unequally yoked together with unbelievers: for what fellowship has righteousness with unrighteousness? and what communion has light with darkness?
 And what concord has Christ with Belial? or what part has he that believes with an infidel?
 And what agreement has the temple of God with idols? for you are the temple of the living God; as God has said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people.
 Why come out from among them, and be you separate, said the Lord, and touch not the unclean thing; and I will receive you.
 And will be a Father to you, and you shall be my sons and daughters, said the Lord Almighty.
American King James Version×). In 1 Corinthians 7:39 1 Corinthians 7:39The wife is bound by the law as long as her husband lives; but if her husband be dead, she is at liberty to be married to whom she will; only in the Lord.
American King James Version×, Paul makes it clear that a Christian is not to marry a person of a different faith. The Living Bible renders this passage as follows: "The [Christian] wife is part of her husband as long as he lives; if her husband dies, then she may marry again, but only if she marries a Christian." God wants us to be happy, and He knows that an interfaith marriage is not going to be as peaceful, joyful and productive as it otherwise would be. Moreover, God is concerned that His child might be influenced by the unbelieving spouse to forsake Him—which happened time and time again in ancient Israel and Judah. And a believer usually is a more effective instrument in doing God's work when he or she has a believing partner, so they can serve as a team.
In this same chapter of Deuteronomy, God promises the nation that if they will obey Him, they will be blessed in their possessions, and He will "take away from [them] all sickness" (7:15; compare Exodus 23:25 Exodus 23:25And you shall serve the LORD your God, and he shall bless your bread, and your water; and I will take sickness away from the middle of you.
American King James Version×). But neither the ancient nor the modern Israelites have lived a lifestyle pleasing to God. And, as a consequence, they were, are, and will be plagued with sicknesses and terrible diseases (compare Leviticus 26:16 Leviticus 26:16I also will do this to you; I will even appoint over you terror, consumption, and the burning ague, that shall consume the eyes, and cause sorrow of heart: and you shall sow your seed in vain, for your enemies shall eat it.
American King James Version×, 21, 25). Although an individual's sickness can be caused by his own sin, such as by smoking, this does not have to be the case. Polluted air, for example, can cause sickness. In this case, the person breathing the air did not sin, but those responsible for polluting the air because of greed—abandoning the responsibility God gave man of caring for the environment—did sin. Indeed, the fact that there is sickness in the world at all is ultimately a result of the general state of mankind being cut off from God due to the sin of Adam and Eve in the Garden of Eden.
Deuteronomy 7:20 Deuteronomy 7:20Moreover the LORD your God will send the hornet among them, until they that are left, and hide themselves from you, be destroyed.
American King James Version×explains that when the Israelites enter the Promised Land, God will fight for them to hand it over to them. We read, "Moreover the Lord your God will send the hornet among them until those who are left, who hide themselves from you, are destroyed." He had similarly told Israel in Exodus 23:27-28 Exodus 23:27-28  I will send my fear before you, and will destroy all the people to whom you shall come, and I will make all your enemies turn their backs to you.  And I will send hornets before you, which shall drive out the Hivite, the Canaanite, and the Hittite, from before you.
American King James Version×: "I will send My fear before you, I will cause confusion among all the people to whom you come, and will make all your enemies turn their backs to you. And I will send hornets before you, which shall drive out the Hivite, the Canaanite, and the Hittite from before you." We will later see that God does send hornets. Indeed, even though Israel fights, their sword does not bring them victory—rather, God does. Moses states: "Therefore understand today that the Lord your God is He who goes over before you as a consuming fire. He will destroy them and bring them down before you; so you shall drive them out and destroy them quickly as the Lord has said to you" (9:3). So God gives them their part to play—but they are not truly responsible for their victory. Following the conquest, He explains, "I sent the hornet before you which drove them out from before you, also the two kings of the Amorites, but not with your sword or with your bow" (Joshua 24:12 Joshua 24:12And I sent the hornet before you, which drove them out from before you, even the two kings of the Amorites; but not with your sword, nor with your bow.
American King James Version×). Sadly, Israel's future disobedience will show just how true this is. For as part of the penalty for forsaking God, Israel will suffer ignominious defeat at the hands of their enemies. "The Lord will cause you to be defeated before your enemies; you shall go out one way against them and flee seven ways before them.... You shall be only oppressed and plundered continually, and no one shall save you" (Deuteronomy 28:25 Deuteronomy 28:25The LORD shall cause you to be smitten before your enemies: you shall go out one way against them, and flee seven ways before them: and shall be removed into all the kingdoms of the earth.
American King James Version×, 29). Thus, trusting in their weapons of war will be utterly useless. True security lies only in God's protection and deliverance.
Today, converted Christians are instructed by God not to fight in war at all (compare Matthew 5:44 Matthew 5:44But I say to you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which spitefully use you, and persecute you;
American King James Version×; Matthew 26:52 Matthew 26:52Then said Jesus to him, Put up again your sword into his place: for all they that take the sword shall perish with the sword.
American King James Version×; Romans 12:20 Romans 12:20Therefore if your enemy hunger, feed him; if he thirst, give him drink: for in so doing you shall heap coals of fire on his head.
American King James Version×; 2 Corinthians 10:3-4 2 Corinthians 10:3-4  For though we walk in the flesh, we do not war after the flesh:  (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;)
American King James Version×; James 4:1-2 James 4:1-2  From where come wars and fights among you? come they not hence, even of your lusts that war in your members?  You lust, and have not: you kill, and desire to have, and cannot obtain: you fight and war, yet you have not, because you ask not.
American King James Version×; 1 John 3:15 1 John 3:15Whoever hates his brother is a murderer: and you know that no murderer has eternal life abiding in him.
American King James Version×). And in the wonderful world to come, when God's Kingdom rules the earth, mankind as a whole will not learn the way of war anymore (Isaiah 2:4 Isaiah 2:4And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more.
American King James Version×).