1 Samuel 15: 2-3, 7-9, 11-30 (NKJV)
7 And Saul attacked the Amalekites, from Havilah all the way to Shur, which is east of Egypt. 8 He also took Agag king of the Amalekites alive, and utterly destroyed all the people with the edge of the sword. 9 But Saul and the people spared Agag and the best of the sheep, the oxen, the fatlings, the lambs, and all that was good, and were unwilling to utterly destroy them. But everything despised and worthless, that they utterly destroyed.
When God gives an instruction, it is necessary to carry out the instruction exactly as told. God knows why he wants it done the way he chose. It is not our place to think for God. When we disobey, we are telling God that we know more than he does and we have to know that there are always consequences.
11 “I greatly regret that I have set up Saul as king, for he has turned back from following Me, and has not performed My commandments.” And it grieved Samuel, and he cried out to the Lord all night. 12 So when Samuel rose early in the morning to meet Saul, it was told Samuel, saying, “Saul went to Carmel, and indeed, he set up a monument for himself; and he has gone on around, passed by, and gone down to Gilgal.” 13 Then Samuel went to Saul, and Saul said to him, “Blessed are you of the Lord! I have performed the commandment of the Lord.”
14 But Samuel said, “What then is this bleating of the sheep in my ears, and the lowing of the oxen which I hear?”
15 And Saul said, “They have brought them from the Amalekites; for the people spared the best of the sheep and the oxen, to sacrifice to the Lord your God; and the rest we have utterly destroyed.”
16 Then Samuel said to Saul, “Be quiet! And I will tell you what the Lord said to me last night.”
And he said to him, “Speak on.”
17 So Samuel said, “When you were little in your own eyes, were you not head of the tribes of Israel? And did not the Lord anoint you king over Israel? 18 Now the Lord sent you on a mission, and said, ‘Go, and utterly destroy the sinners, the Amalekites, and fight against them until they are consumed.’ 19 Why then did you not obey the voice of the Lord? Why did you swoop down on the spoil, and do evil in the sight of the Lord?”
20 And Saul said to Samuel, “But I have obeyed the voice of the Lord, and gone on the mission on which the Lord sent me, and brought back Agag king of Amalek; I have utterly destroyed the Amalekites. 21 But the people took of the plunder, sheep and oxen, the best of the things which should have been utterly destroyed, to sacrifice to the Lord your God in Gilgal.”
22 So Samuel said:
As in obeying the voice of the Lord?
Behold, to obey is better than sacrifice,
And to heed than the fat of rams.
23 For rebellion is as the sin of witchcraft,
And stubbornness is as iniquity and idolatry.
Because you have rejected the word of the Lord,
He also has rejected you from being king.”
26 But Samuel said to Saul, “I will not return with you, for you have rejected the word of the Lord, and the Lord has rejected you from being king over Israel.”
27 And as Samuel turned around to go away, Saul seized the edge of his robe, and it tore. 28 So Samuel said to him, “The Lord has torn the kingdom of Israel from you today, and has given it to a neighbor of yours, who is better than you. 29 And also the Strength of Israel will not lie nor relent. For He is not a man, that He should relent.”
30 Then he said, “I have sinned; yet honor me now, please, before the elders of my people and before Israel, and return with me, that I may worship the Lord your God.”
As in the case of Saul, God said in verse 11 that Saul had turned back from following him, and had not performed his commandments. When we disobey our parents, elders, bosses, we know the consequences that comes with it. There are some disobedience that cannot be rectified because the deed is already done. Saul disobeyed God because man told him not to do what God instructed him to and he was afraid of them. By listening to his army, he put them before God. Peter and Paul asked in Acts 4:19
The disobedience of Saul led to him being replaced as king over Israel and it was a big lose.
And be gracious to me;
And give me peace.”’