1 Samuel 14 - 15

The Lord brings victories over the Philistines and the Amalekites, but Saul acts foolishly, and then disobeys the command of the Lord in not killing the king of the Amalekites, and in taking plunder.  Samuel confronts Saul, but he has nothing be excuses, so it’s make clear what the Lord expects of us all…

So Samuel said: "Has the LORD as great delight in burnt offerings and sacrifices, As in obeying the voice of the LORD? Behold, to obey is better than sacrifice, And to heed than the fat of rams.
- 1 Samuel 15:22 NKJV

Samuel then tells Saul that the Lord has rejected him from being king in Israel, and will place it on a man who is better.