What does 1 Samuel 15:31 mean?

It's unclear exactly why Samuel changes his mind and agrees to go with Saul to honor God in front of the people. Samuel first told Saul that he would not go with him (1 Samuel 15:26). Now that Saul fully understands that the Lord's decision to remove him as king will not be changed, Samuel agrees to honor Saul by being present when Saul bows before the Lord.

Commentators speculate that Samuel did not want to disrupt the stability of the nation by publicly indicating that Saul had lost the Lord's approval. Perhaps Samuel cared for Saul and was sympathetic to him; he will grieve over the man he anointed as Israel's first king (1 Samuel 15:35). A highly likely reason is that Samuel plans to finish the task Saul has failed to do. Samuel will kill the king of the Amalekites in obedience to God's command, making a graphic and public point about the need to obey the Lord's will (1 Samuel 15:32–33).