Deuteronomy 7:3 Neither shalt thou make marriages with them; thy daughter thou shalt not give unto his son, nor his daughter shalt thou take unto thy son. 4 For they will turn away thy son from following me, that they may serve other gods: so will the anger of the Lord be kindled against you, and destroy thee suddenly.
[Patriarchs & Prophets pp 369>370] Idolatry and all the sins that followed in its train were abhorrent to God, and He commanded His people not to mingle with other nations, to “do after their works“, and forget God. He forbade their marriage with idolaters, lest their hearts should be led away from Him. It was just as necessary then as it is now that God's people should be pure, “unspotted from the world.” They must keep themselves free from its spirit, because it is opposed to truth and righteousness. But God did not intend that His people, in self-righteous exclusiveness, should shut themselves away from the world, so that they could have no influence upon it.
Like their Master, the followers of Christ in every age were to be the light of the world. The Savior said, “A city that is set on an hill cannot be hid. Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house”—that is, in the world. And He adds, “Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.” Matthew 5:14-16. This is just what Enoch, and Noah, Abraham, Joseph, and Moses did.
It is just what God designed that His people Israel should do. It was their own evil heart of unbelief, controlled by Satan, that led them to hide their light, instead of shedding it upon surrounding peoples. It was that same bigoted spirit that caused them either to follow the iniquitous practices of the heathen or to shut themselves away in proud exclusiveness, as if God's love and care were over them alone.
Matthew 5:13 Ye are the salt of the earth: but if the salt have lost his savor, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.
May The Lord add His blessing to the study of His word. God bless!