1. DO IT RIGHT THE FIRST TIME OR YOU'LL BE SORRY LATER.
Deuteronomy 1:2,3 - "It is eleven days' journey from Horeb by way of Mount Seir to Kadesh Barnea. Now it came to pass in the fortieth year, in the eleventh month, on the first day of the month, that Moses spoke to the children of Israel according to all that the LORD had given him as commandments to them."
Those verses are so sad to read! It should have taken a relatively short amount of time (weeks, not years) to get from Sinai to the Promised Land. Instead they disbelieved and ended up taking nearly four decades to get to their destination! Their disobedience cost them a generation in the land and over one million deaths. Doing something right the first time is of great importance and benefit.
2. TO SAY SOMETHING WITH PASSION DOESN'T NECESSARILY MAKE IT TRUE.
Deuteronomy 1:27 - "And you complained in your tents, and said, 'Because the LORD hates us, He has brought us out of the land of Egypt to deliver us into the hand of the Amorites, to destroy us."
They had deceived themselves if they really believed that Jehovah hated them. It was true that God punished them frequently for their rebellion, but they needed correction! He wanted them to prosper and He labored toward that end. It is good to be full of zeal, but words spoken passionately aren't necessarily any more true than those spoken in a soft monotone.
3. CHILDREN OFTEN SUFFER FOR THE SINS OF THEIR PARENTS.
Deuteronomy 1:39 - "Moreover your little ones and your children, who you say will be victims, who today have no knowledge of good and evil, they shall go in there; to them I will give it, and they shall possess it."
It is true that the children would one day lay hold of the Promised Land but, in the meantime, would have to suffer with their parents wandering in the wilderness. Many children today also suffer for the foolish and immoral decisions of their parents.
4. HAVING MATERIAL SUFFICIENCY DOES NOT NECESSARILY PRECLUDE MURMURING.
Deuteronomy 2:7 - "For the LORD your God has blessed you in all the work of your hand. He knows your trudging through this great wilderness. These forty years the LORD your God has been with you; you have lacked nothing."
God provided them with their necessities via miracles, yet they were not content. They were ungrateful and grumbled and complained regularly. Contentment is something we must learn; it is a state of mind. The apostle Paul learned to be content in whatever state he found himself (whether he lacked or had abundance; Phil. 4:11,12). Those who fail to be satisfied with God's provision will likely fall prey to the sin of complaining (cf. Phil. 2:14).
5. GOD HAS NEVER ALLOWED MAN TO ALTER HIS WORD.
Deuteronomy 4:2 - "You shall not add to the word which I command you, nor take from it, that you may keep the commandments of the LORD your God which I command you."
Similar sentiments can be found in other Scriptures - "Whatever I command you, be careful to observe it; you shall not add to it nor take away from it" (Deut. 12:32). "Do not add to His words, lest He rebuke you, and you be found a liar" (Prov. 30:6). "For I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book; and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book" (Rev. 22:18,19). Since God has given us all the information we need in Scripture (cf. II Tim. 3:16,17; II Pet. 1:3), to attempt to change His word is an attack against Him and is strongly forbidden. To change His word is to fall under His curse (cf. Gal. 1:6-9).