That point is made clear in the narrative of King Saul. In 1 Samuel 15, the prophet Samuel delivered a message from God for King Saul. God told Saul to completely destroy the nation of Amalek. This destruction was to be divine retribution for that nation's attack on the Israelites during the Exodus. Saul did defeat Amalek. But he stopped short of complete destruction. Saul took the king of Amalek alive and kept the best livestock. After setting up a monument for himself, Saul proceeded to take the livestock he had captured to Gilgal, in order to sacrifice those creatures to God. The only problem was that was not what God wanted Saul to do. God told Samuel that Saul would be removed as king and another would take his place. When Samuel confronted Saul, he told him:
"Behold, to obey is better than sacrifice, and to heed than the fat of rams. For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry." (1 Samuel 15:22-23, NKJV)
This very blunt statement tells us two reasons obedience is important to God.
One reason obedience is important to God is because obedience is better than religious ritual. Saul was willing to sacrifice the best of the spoils of war to God. But God was not interested in those sacrifices. God was interested in obedience. Saul had only partially completed the task God commanded him to do. Instead of completing the task, Saul thought he had a better idea. Somehow, Saul thought that he could please God more by doing things his way than by doing things the way God said. Although he would never have consciously thought such a thing, Saul thought his idea was better than God's command. This act of arrogance transformed Saul's sacrifice into an act of defiance against Almighty God. God was not pleased. Obedience is better than religious ritual.
How often do we do the same thing? We develop our own ideas about what is right or wrong, or what will please God without consulting or following the clear teachings of God's Word. It is as if we come to God singing 'I Did It My Way' instead of 'I Surrender All.' God is not impressed. God told us how He wants us to approach Him. We must approach God on His terms, not our own. Our salvation is established by God's grace through faith in Jesus Christ, not by good works (See my page titled ETERNAL LIFE.); however, the quality of our fellowship with God and our usefulness in His kingdom work depends on our obedience to His commands. The sacrifice God is most interested in is a surrendered life. Without that, all other sacrifices are useless.
Another reason obedience is important to God is because disobedience is treason against God. Saul's disobedience was described as rebellion and stubbornness. Indeed, Saul's disobedience was rebellion against God, because he simply refused to do what God said. That rebellion was compared to witchcraft. When Saul refused to serve God, he inadvertently served the devil, just as much as if he had participated in the occult. Also, Saul's stubbornness is described as iniquity (sin) and idolatry. Saul's failure to complete the task God had given him was a sin. Saul's stubborn attitude was idolatry, because he placed more value on his own desires than God's commands. He placed himself above God. He became his own idol. Outwardly he worshipped God, but inwardly, without realizing it, he worshipped himself. Saul was leading the people to disobey God. God would not allow that to continue. Therefore, God decided to remove Saul from his position of leadership.
We often make the same mistake Saul made. We do not think of our actions as being rebellious. We simply think we have a better way of doing things than the antiquated ways of the Bible. But our failure to completely obey God has a profound effect on our fellowship with God. How can we have good fellowship with God when we are living in opposition to Him? We cannot. We must obey God completely. When we fail, we must quickly repent of our sins and re-align ourselves with God in order to restore our fellowship with Him.
God desires fellowship with us. He has a purpose for us. If we will follow Him, we will enjoy fellowship with God and discover our God-given purpose for our lives.
