Numbers 15  The rebellion has brought Israel to Hormah, run down and struck by the Amalekites and the Canaanites.  They would not enter the promised land of milk and honey until 40 years have passed and all the rebellious people had died.

But, God immediately begins talking to them about things that they will do "when" they enter the land.
When you enter you will offer sacrifices according to the law.
When you enter you will treat the aliens the same as the nationals.
When someone sins unintentionally, atonement will be made so that this sin will be forgiven.  Whether for the whole congregation or an individual... An error, a mistake, an unintended sin made in ignorance - can be atoned for and forgiven.
But, a defiant sinner, one who blasphemes the Lord, who despises the word, who breaks the Law - that person is to be cut off from the people. He is to be destroyed.  No atonement will be made.  No forgiveness will be offered.  The guilt remains on him.

This is put to the test immediately.  ( verses 32 -36)  A man goes out on the sabbath and gathers wood.  He is brought before Moses and the Lord passes judgment - stone him to death.  And they obey.

Verses 38-41  The Lord tells Moses to have the people make tassels with a cord of blue for the corners of their garments. It is to remind them of God's commandments, "so as to do them and not follow after your own heart and your own eyes, after which you played the harlot, in order that you may remember to do all My commandments, and be holy to your God.  I am the Lord your God who brought you out from the land of Egypt to be your God; I am the Lord your God." 

The Lord reminds His people that He has chosen them;
He has redeemed them;
 and He is still their God.  
His covenant with them is unchanged.  Sin is still sin.  The Law is still the Law.
He wants them to be holy.  To walk in His ways and be obedient to His Words.
Yes, mistakes will be made, sin will happen, but there is a way to forgiveness through atonement offerings.
But, rebellion will be punished.  Following your own sinful hearts and wicked desires will result in death.

Remember... He tells them.  Remember what the Word says.  Remember as you put on your clothing and see the blue cord on your robe.  Remember as you bring your offerings.  Remember and do not rebel any more.

And Jesus tells us also - Remember.  Remember my death.  Remember the atonement offering that was given through My body and My blood.  An atonement offering greater than any offered through the years, for it is an atonement for all sin. 
An atonement offering that is offered by our Great High Priest, Jesus Christ.
" Hence, also, He is able to save forever those who draw near to God through Him, since He always lives to make intercession for them. For it is fitting that we should have such a high priest, holy, innocent, undefiled, separated from sinners and exalted above the heavens; who does not need daily, like those high priests, to offer up sacrifices for His own sins and then for the sins of the people, because this He did once for all when He offered up Himself." Hebrews 7:25-27

Mighty God, our God and Father,  Holy is Your Name.  I AM, LORD, Jehovah.. You are merciful and gracious, slow to anger and great in lovingkindness.  You have shown us Your goodness and love through the atonement offering of Your Only Son, our Lord, Jesus Christ.  His body broken and His blood spilled out.. so that our sins can be forgiven.  Let our hearts be in awe of this Truth.  Let us bow down and worship You.  Help us to remember and never forget what You have done for us. To remember what You desire for us.  To trust You to bring us to the Promised Land of heaven, where we will be with You eternally through Christ our Lord. In His Name we come.  Fill us with Your Spirit today, that we might fully obey Your Word in His power, to Your Glory. Amen.