Deuteronomy 4

1 Moses encourages the Israelites to listen to and obey the commands of God. They will only take the land by the power of God, and God was pleased to help them when they maintained good relationships with Him. Since people are under God's authority, obedience to His commands is a vital part of our relationship with Him.
2 The laws that Moses spoke of were God's laws. It was very important that the people not decide that certain laws were no longer important. It was also important that people not simply start making up their own laws. Both activities elevate people over God and might be considered blasphemous.

By Jesus' time, the Jews had developed many of their own traditions and elevated their status above the commands of God. They also reinterpreted God's laws so that they could "obey" and "break" them at the same time (Mat 15:3-9).

Some claim that Christians are hypocritical because they believe the whole Bible but do not do all the things commanded by God in the Old Testament. Jesus fulfilled all the sacrificial commands in His death on the cross, so for believers to continue in sacrificing animals is an insult to Jesus' necessary and sufficient sacrifice (Heb 9:24-26). Jesus also fulfills many physical defilement laws like the dietary restrictions (Mat 15:11-20). The moral and behavioral laws still stand, but even there God forgives those who break a law but then repent (1 John 1:9).

3 This refers to Num 25:1-9 where 24,000 people died in God's judgment against idol worship.
4 The survivors were their own object lesson. They survived the plague because the held to God's laws. Thus, they should continue to follow them so that they will avoid God' wrath.
5 When God commands us to do (or avoid) something, He expects to be obeyed. His laws are both beneficial to people and beneficial to our relationship with Him, so we do well to follow them.
6 The Law was not intended to be a burden to the people. Instead, it was to give them wisdom.
7 God had graciously made the Israelites keepers of His law because He cared for them. Among the nations, no one else has had that honor.
8 No other nation had laws based on God's word. Thus, God's law could impart righteousness because it would enhance one's relationship with God. Note, however, that if the law were followed without any relationship with God, then pleasing His would be futile.
9 Even when we have learned and experienced great things, we tend to forget them. It takes great effort to remember and obey. We often require God's help to accomplish this. God's people must make a concerted effort to teach their children about Him. We can not take it for granted that they will simply see and imitate us. Even more importantly, they need to make their own commitment of faith. A parent can not have faith for their child; the child must develop his own. A person's family should be their most important ministry field.
10 The Israelites of that day were primary witnesses, so it was important that they conveyed what they saw to their children. It is implied that the children would not see similar great miracles. Those who did see great miracles must testify about them lest the evidence be lost forever.
12 Moses emphasized that God did not appear in a particular shape. If He had, the people were much more likely to design an image of it and eventually worship the image as an idol. God is a spirit Being who supercedes the universe. It is not possible to capture His characteristics in an artistic portrayal.
13 There were many other laws and rules associated with the covenant, but the Ten Commandments are the summery of them all. Jesus would later sum up both the Law and the Prophets in two commands (Mat 22:37-40).
14 When a teacher teaches students, he expects them to learn and apply what they learn. Since Moses was teaching God's commands, it was even more important that the students, the Israelites, commit to following them.
32 Since creation until that time, God had never spoken to an entire nation.
33 The holiness of God could destroy those who saw or heard a theophany (a physical manifestation of God's presence). The sin-corrupted flesh can not stand before the pure and holy God. The Bible records several instances where God had mercy on particular listeners so that they were not destroyed.
34 When one people group moves into a territory with another people group, their identities typically merge within a few generations. Israel had remained separate from the Egyptians for 400 years. Then God separated the Israelites from the Egyptians -- a feat that had never been done before.
35 God appeared to the Israelites in very real ways: vocal, visual, and with great deeds. There should be no doubt in their mind that God exists and He is the only God. Multi-god religions are man made. Other gods exist only in the imagination.
37 God did these things because of the special relationship He had with several of their ancestors.
39 God not distant -- He interacts with all His creation on a moment-by-moment basis.
40 Because God did these great things for Israel and because He is always near, the people should obey God's commandments. The combination of love, gratitude, respect, fear, and reverence encourages people to obey God.