Va'etchanan - Sheini
I Know I Told You This Before, But...
Moshe told the Jews to be careful in adhering to the mitzvos, which God gave to elevate them. If they follow His laws scrupulously, they will be respected by the other nations. Israel has a unique relationship with God and only they have the Torah. They only have to stay true and carefully educate the next generation about the things that were taught at Sinai.
Moshe reminded the nation about the revelation at Sinai, where they stood by the mountain and personally heard God. He gave the Ten Commandments, which He also had engraved on the two stone tablets. There were no images at Sinai, Moshe pointed out, because idols are not an acceptable form of worship. The people are not to worship the creatures of nature or the celestial bodies - only God, Who took them from Egypt to be His people. (Moshe tells the people that he's reiterating this point because he won't be entering the land with them.)
Moshe warned the people that after a generation or two, they might get complacent and slack off, worshipping idols. He called upon Heaven and Earth as witnesses that, if they do, that's the very thing that will cause them to be driven from the land. They'll be scattered among the nations and only a small remnant will endure. They will, however, eventually find their way back to God. When they call to God from the nations of their exile, He will welcome them back. He will never permit them to be eradicated.
Just look at the unprecedented relationship that the Jews have with God! Has any other nation ever experienced God en masse and lived to tell the tale? Has any nation ever been extracted from the midst of another nation amid miracles and wonders like when God took the Jews out of Egypt? They have been shown enough to realize that God is the only Power - there is no other. (Verse 34 may be familiar from the Passover Haggadah; verse 35 may be familiar from the song "Atoh Horaisa.")
God took Israel out of Egypt because of His special bond with their Forefathers. That's why He will also drive out the Canaanite nations. So don't blow it. (That last part is rather freely paraphrased, but that's the gist of it.)