1 Samuel 15 - There are a number of lessons to be learned from this chapter. One is: God gives us more than just a second chance to correct our lives. Already Saul has been told that God will look for someone else. That should have been a great motive to want to live out the rest of his life seeking to please the Lord. But, Saul just couldn't get passed his ego and lack of trust in God. He had been given specific instructions, but he chose what he thought was best. He thought pleasing God with "great sacrifices" was more important than obedience. We all need to keep in mind that God is not impressed with our worship on Sunday if we're living compromising lives during the week.
1 Samuel 16 - God fulfilled His word to Samuel that He would seek a man after His own heart. And He chose a boy! That ought to give every young person the motivation to focus their love and attention on God in their youth. God doesn't need "old and experienced" people only to do His will. He looks for those whose hearts yearn to please God and who will take on any challenge to show God's power.
1 Samuel 17 - And here comes a "Giant Challenge!" Goliath was big. But David knew that God was bigger! Someone said years ago that Saul and his army felt Goliath was "too big to hit, whereas David felt he was too big to miss!" What was the reason for Saul's fear and David's confidence? Saul kept his eyes on his enemy and was afraid. David kept his eyes on his God and was empowered. David knew God and he knew God would give him the victory! Of course, we can see God's plan in showing Israel that their next king would honor the Lord and was not afraid to take a stand for God even if he was going to have to stand alone!