Why did Samuel rebuke Saul in 1 Samuel 13?

Samuel rebuked Saul in 1 Samuel 13 because Saul acted impulsively by offering a burnt sacrifice to God without waiting for Samuel to arrive, violating God's command. This act demonstrated a lack of faith and patience, undermining Samuel's role as God's prophet and priest. As a result, Samuel informed Saul that his kingdom would not endure, and God had chosen another leader to replace him.