The Philistines assembled to fight Israel. Saul and Israelites were waiting for Samuel to come and offer offerings to the Lord. They wanted guidance from Samuel as to whether they should go for war or not. Saul waited for seven days, the time-period mentioned by Samuel. But Samuel did not come. People started to go away from Saul because of all this. They were afraid of the Philistines. When Saul saw all this, instead of waiting further for Samuel, he ordered that burnt and fellowship offerings be taken to him. Only priests were supposed to offer burnt offerings, but Saul went ahead and offered it.
Just as he finished, Samuel came and he asked ‘what have you done’. Saul replied ‘when I saw that men were scattering, and you did not come at the said time, and the Philistines were assembling, I thought the Philistines will come against me and I haven’t sought the Lord’s favor, so I felt compelled to offer the burnt offering.
Samuel said, ‘You acted foolishly. You did not obey God. Because of this you will lose your kingdom. God has selected a man after His own heart and appointed him as the leader of His people.” Even though he won the battle with Philistines, he lost his kingdom.
“Then the word of the Lord came to Samuel, I am grieved that I have made Saul king because he has turned away from me and has not carried out my instructions” 1 Samuel 15:10