What does 1 Samuel 15:10 mean?

In the previous chapter, Saul wanted to hear from God about an important military decision. The Lord's refusal to respond suggested to Saul that someone among the Israelites was guilty of sin (1 Samuel 14:36–39).

Now, when Saul is plainly and clearly guilty of sin himself, the Lord does not wait to be called upon. God initiates contact with Samuel about Saul's sin and the consequences. The phrase, "The word of the LORD came to" describes God's process of revealing Himself to people. So, the Lord seems to be the one who personally delivers to Samuel the news that Saul has failed to kill the king of the Amalekites (1 Samuel 15:3, 9) and that many of the animals have been taken as plunder. This is disobedience because the Lord's orders were to entirely erase the Amalekite nation.