We read in the Old Testament of how God gave the Ten Commandments and one of them being "Thou shalt not kill." Soon after that God sent the Israelites to battles in which they ended up slaying thousands of their enemies.

 God commanded whole cities to be destroyed; including women and innocent young children. All the possessions of the enemies were to be destroyed.  

 In contrast to that in the New Testament Jesus said His kingdom was not of this world, if it was He would fight back. Yet the Israelites fought one battle after the other in order to inherit the Land of Canaan. 

 A man was stoned to death because he was found picking up sticks on a Sabbath; on a day which God commanded that no work should be done.  

 In the New Testament Jesus and His disciples walked through a corn field and the disciples picked and ate from the corn. According to God's Law should these disciples not been stoned as well?  

 According to the old law any woman who was caught in adultery was to be stoned, but in the New Testament Jesus let the adulteress woman go when they brought her before him.

 In the Old Testament Abraham, Job, David, Solomon and many others were given material wealth as a sign that God was pleased with them. God was pleased with Jesus more than with any other that ever lived, yet Jesus was homeless. Jesus even said that it would be easier for a camel to walk through the eye of a needle than for a rich man to enter into heaven.

 Are these contradictions, did God change his mind, or did He realize that the Ten Commandments weren't working and a change of plans was needed. 

 The answer is God knew before He gave the Commandments that no one would be able to obey them all. He gave us the Ten Commandments to show us that we would never be perfect without Him. I believe God purposefully did this so that when the Holy Spirit would come, we'd all see the power of the Holy Spirit when He keeps us from sinning.  

 It seems mind boggling though that a good God would allow such violent wars and so many stonings for disobeying one commandment. 

 To understand why God commanded what He did, we need to understand the purpose of the Old and New Testaments. When we understand the purpose, we can see that they are parallel to each other and go hand in hand.  

The purpose of the Old Testament was that God wanted the human race to understand how wicked we really are apart from God. People didn't have direct communication with God in those days. When a person needed guidance or forgiveness, instead of going to God they had to go to the priests. 

 They had no continuant guidance from God and so they kept falling into sins, no matter how hard they tried to obey. 

 The purpose of the New Testament was to show us that when we are born of the Holy Spirit we will have the power and strength to resist temptation and avoid evil. The Holy Spirit will never leave nor forsake us, but guides us continually. 

 Also the Old Testament speaks of the physical, and the New Testament speaks of the Spiritual.  

 Jesus said to his disciples that unless they were more righteous than the Pharisees they would not enter into heaven. The Pharisees kept all the physical laws which God had ordained in the Old Testament. According to that they should have been the first ones to enter in; but what kept them from entering in was the fact that their hearts were not pure. They harbored in their hearts anger, hatred, jealousy and other detestable sins which could not be seen on the outside, which later led them to crucify Jesus. 

 Jesus went on to say that any one who is angry at his brother has already committed murder in his heart and is guilty of hell-fire. Any one who lusts after a woman or man has already committed adultery in his or her heart and is guilty of hell-fire.  

 The Ten Commandments which were physical in the Old Testament were now made into Spiritual Commandments. When we keep our minds pure with the help of the Holy Spirit, we'll never lust after that woman or man; once we learn to love everyone we'll never have to worry about murdering anyone; and likewise with all the other commandments. (Thus the phrase we are free from the law.) 

 The Israelites were instructed to violently destroy their physical enemies if they wanted to enter into Canaan; in the same manner we are to destroy our spiritual enemies (sin) if we want to enter into the kingdom of heaven. 

 When people were stoned it represented our spiritual death; every time we fall into sin we die spiritually and cannot enter into heaven until we have confessed that particular sin. 

 The physical wealth given in the Old Testament represented the Spiritual wealth given in the New Testament such as love, joy, peace, patience, kindness, and the list goes on. I believe Jesus was the richest man that ever walked on the face of the earth because He had all of God's spiritual blessings from day one! 

 If God had not given us the physical first we may not realize or admit to how easy it is to fall into sin. We can hide our thoughts to a certain degree, but our actions are seen by all men. The Old Testament was necessary in order for us to understand that we need the Holy Spirit in our lives at every moment of every day.