Question: "What does it mean that Saul is also among the prophets?"
Answer: When Samuel anointed Saul as the first king of Israel, he predicted that Saul would prophesy, saying, “The Spirit of the LORD will come powerfully upon you, and you will prophesy with them; and you will be changed into a different person” (1 Samuel 10:6). This prediction came true on that same day.
We read in verses 10–12, “When [Saul] and his servant arrived at Gibeah, a procession of prophets met him; the Spirit of God came powerfully upon him, and he joined in their prophesying. When all those who had formerly known him saw him prophesying with the prophets, they asked each other, ‘What is this that has happened to the son of Kish? Is Saul also among the prophets?’ A man who lived there answered, ‘And who is their father?’ So it became a saying: ‘Is Saul also among the prophets?’”
Years later, as king, Saul sent three different groups of servants who prophesied to David. When Saul personally traveled to this location, he again prophesied: “Saul went to Naioth at Ramah. But the Spirit of God came even on him, and he walked along prophesying until he came to Naioth. He stripped off his garments, and he too prophesied in Samuel’s presence. He lay naked all that day and all that night. This is why people say, ‘Is Saul also among the prophets?’” (1 Samuel 19:23–24). Who were these other prophets?
Though a group called “the sons of the prophets” existed much later in the time of Elijah and Elisha (1 Kings 20:35; 2:3–15; 4:1, 38; 5:22; 6:1), little is known about “the prophets” mentioned in Saul’s time. During these times, prophets were often associated with musicians who sang praise to God. In Samuel’s original prediction of the event, he mentioned “a procession of prophets coming down from the high place with lyres, timbrels, pipes and harps being played before them” (1 Samuel 10:5). It is likely this was group of musicians from Gibeah who prophesied before the Lord. The tabernacle may have been at that location, though it is uncertain. If so, however, it is likely this group of musicians consisted of Levite men ages 20 to 50 who were permitted to serve in the tabernacle.
Beyond this, little is known. The facts that Saul prophesied among them and it was considered odd suggest these prophets were not from his tribe or area (and perhaps that Saul was not a musician, though this is uncertain). The most likely scenario is that these Levite musicians were together worshiping and prophesying with music and that Saul, by the inspiration of the Spirit, was caught up in their activity. This behavior was a confirming sign of Saul’s anointing as king.
It is also interesting to note that Saul would later ask for a person who played the harp to be brought before him (1 Samuel 16:22–23). God raised up David for this role, the man who would follow Saul as the next king.