'Then Saul fell at once full length upon the ground, filled with fear because of ...

In this question, we are given a passage from the Bible describing an event that happened to Saul. The question then asks us to identify what Samuel said to Saul that caused him to fall to the ground in fear.

Option A suggests that Saul was rebuked for sparing Agag, Option C suggests that Saul was condemned for offering a sacrifice before Samuel arrived, and Option D suggests that Samuel was invoked from the dead. However, the correct answer is Option B, which states that Samuel told Saul that God had rejected him and had chosen David to be king.

This event is significant because it marks a turning point in Saul's reign as king of Israel. Samuel was a prophet who anointed Saul as king, but now he tells Saul that God has rejected him and chosen someone else to be king. This ultimately leads to Saul's downfall and David becoming the next king of Israel.

This passage also highlights the importance of obeying God's commands and the consequences of disobedience. Saul's disobedience led to his rejection by God and his eventual downfall.

In summary, the correct answer to this question is Option B, which states that Samuel told Saul that God had rejected him and had chosen David to be king. This event marked a significant turning point in Saul's reign and highlights the importance of obeying God's commands.