2 Samuel 12:1-23
"David's anger was greatly kindled against the man, and he said to Nathan, "As the LORD lives, the man who has done this deserves to die."  2 Samuel 12:5

The LORD sent Nathan with His Word to confront David's sin.  David immediately knew what Nathan described was wrong and deserved punishment.  "Thou shalt not steal."  (Exodus 20:15)  Nathan instantly responded, "You are the man!"  God's Word always succeeds in accomplishing His purpose. (Isaiah 55:11)  His Word truly is "living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart." (Hebrews 4:12)  

David's sin is so much greater than the man in Nathan's story.  David stole, committed adultery (Exodus 20:14) and murdered (Exodus 20:13).  But the grievous nature of David's sin is compounded by the abundant, plentiful grace God had given him.  Look at all God provided for David in verse eight.  If that were not enough, God said, "If this were too little, I would add to you as much more."  David had returned God's good with evil.  With such evidence of the LORD's goodness to David, we can understand David's response "I have sinned against the LORD."  

It seems an appropriate time to Scripturally define sin.  1 John 3:4 says, "Sin is lawlessness."  Romans 4:15 says, "Where there is no law there is no transgression."  Therefore, sin is the transgression (violation) of God's law.  There are many other Biblical definitions of sin, but the combination of these two verses fits David's actions very well.  I listed three specific commandments David violated but if you think about it, you will realize he broke several more.  

To understand the severity of David's sin, let's examine God's accusation against him.  In verses 9-10, God says David despised both Him and His Word.  Numbers 15:31 says, "Because he has despised the word of the LORD and has broken his commandment, that person shall be utterly cut off; his iniquity shall be on him."  In the previous two verses unintentional and intentional (high hand) sins are discussed.  (Clicking on Day 127 will provide a detailed explanation of the difference.)  In 1 Samuel 2:30-31 the LORD promised to cut off Eli's family because he and his sons despised Him.  2 Chronicles 36:16 says, "They kept mocking the messengers of God despising his words and scoffing at his prophets, until the wrath of the LORD rose against his people, until there was no remedy."  In addition to that, Exodus 21:12 says, "Whoever strikes a man so that he dies shall be put to death."  Nathan told David "You have struck down Uriah the Hittite with the sword...and have killed him with the sword of the Ammonites."  

Isn't it astonishing Nathan then told David, "The LORD also has put away your sin; you shall not die"?  On what basis could a just God put such grievous sin away?  

In 2 Samuel 7:11-16, God entered into an unconditional covenant with David; "The LORD will make you a house...I will raise up your offspring after you...and I will establish his kingdom...I will establish the throne of his kingdom forever...your house and your kingdom shall be made sure forever before me.  Your throne shall be established forever."  If you will notice, the LORD did not tell David, "If you do...then I will do..."  This covenant is an "I will" covenant, like the one God made with Abraham in Genesis 17:6-8.  In the Abrahamic covenant, five times the LORD says "I will."  Obviously, the fulfillment of the Davidic covenant is Christ Jesus.  David had many sons who sat on the throne of Israel, but none except God's Son in the flesh (Romans 1:3) could fulfill the eternal component of the covenant.