1 - following the commands seems to be a condition upon which Israel will take possession of the land.
2 - Moses warns against adding or subtracting to the law
Matthew Henry's commentary has this to say about v. 2:
He charges them to preserve the divine law pure and entire among them, v. 2. Keep it pure, and do not add to it; keep it entire, and do not diminish from it. Not in practice, so some: "You shall not add by committing the evil which the law forbids, nor diminish by omitting the good which the law requires." Not in opinion, so others: "You shall not add your own inventions, as if the divine institutions were defective, nor introduce, much less impose, any rites of religious worship other than what God has appointed; nor shall you diminish, or set aside, any thing that is appointed, as needless or superfluous." God's work is perfect, nothing can be put to it, nor taken from it, without making it the worse. See Eccl. 3:14. The Jews understand it as prohibiting the alteration of the text or letter of the law, even in the least jot or tittle; and to their great care and exactness herein we are very much indebted, under God, for the purity and integrity of the Hebrew code. We find a fence like this made about the New Testament in the close of it, Rev. 22:18, 19.
This instruction is repeated through out scripture in several places:
Deuteronomy 12:32
"See that you do all I command you; do not add to it or take away from it."
Ecclesiastes 3:14
"I know that everything God does will endure forever; nothing can be added to it and nothing taken from it. God does it so that men will revere him."
Galatians 3:15
"Brothers, let me take an example from everyday life. Just as no one can set aside or add to a human covenant that has been duly established, so it is in this case."
What God has given us is perfect and holy. Perhaps if I can finally get to the point that I believe that all instruction necessary for righteousness has already been given me and that I cannot add to or take away from my inheritance in both the Law and the fulfillment of the Law, I would learn to live a life not constantly plagued with self doubt. Ultimately, as Paul mentions in the Galatians passage, the totality of the covenant is contained in the promise given to Abraham and its fulfillment in Christ.
3,4 - Reminds the Israelites about the consquences of turning to idols and the rewards of remaining faithful. (Numbers 25:1-9)
There entire remained of the old testament seems a proof text for this verse.
5 - Moses taught the Israelites God's law so they would know His law when they entered the land.
It seems that an assumption could be made the this passage implies that if the Israelites could not learn the Law while wandering in the desert with food and water supplied for them, then they certainly wouldn't get it through their skulls once the reached the point of fighting for and maintaining their land. What if they hadn't wasted their time in the desert? Personal life application....proably!
6 - By keeping the Law the Israelites would show to the other nations how wise and understanding they are.
This I find interesting...in the Old Testament it was through obedience to the Law that Israel would glorify their God and draw the attention of the Nations. In the New Testament the Law has been replaced by Love as the medium through which a lost world will find redemption.
7 - Moses reminds the Israelites how special they are to have a God who is near to them whenever they pray unlike any other nation.
8 - And that the laws and decrees show the greatness of the Israeli nation.
Not their land, not their amazing victories, not their wealth or fame but their law.
It amazes me that no matter what area of scripture I dive into, or how opaque the text is at first reading, it is always so rich upon contemplation and study, and I know I have just scratched the surface of the knowledge and revelation it contains for me.
So today's lyrics are from Hillsong:
From the Inside Out
A thousand times I've failed
Still your mercy remains
And should I stumble again
Still I'm caught in your grace
Everlasting, Your light will shine when all else fades
Never ending, Your glory goes beyond all fame
In my heart, in my soul, Lord I give you control
Consume me from the inside out Lord
Let justice and praise become my embrace
To love You from the inside out
Your will above all else, my purpose remains
The art of losing myself in bringing you praise
Everlasting, Your light will shine when all else fades
Never ending, Your glory goes beyond all fame
In my heart, in my soul, Lord I give you control
Consume me from the inside out Lord
Let justice and praise become my embrace
To love You from the inside out
Chorus 2x
Everlasting, Your light will shine when all else fades
Never ending, Your glory goes beyond all fame
And the cry of my heart is to bring You praise
From the inside out Lord, my soul cries out