10 When Saul and his servant arrived at Gibeah, they saw a group of prophets coming toward them. Then the Spirit of God came powerfully upon Saul, and he, too, began to prophesy. 11 When those who knew Saul heard about it, they exclaimed, "What? Is even Saul a prophet? How did the son of Kish become a prophet?" 12 And one of those standing there said, "Can anyone become a prophet, no matter who his father is?" So that is the origin of the saying "Is even Saul a prophet?"
Matthew Henry's Commentary on 1 Samuel 10:10-12
Commentary on 1 Samuel 10:9-16
(Read 1 Samuel 10:9-16)
The signs Samuel had given Saul, came to pass punctually; he found that God had given him another heart, another disposition of mind. Yet let not an outward show of devotion, and a sudden change for the present, be too much relied on; Saul among the prophets was Saul still. His being anointed was kept private. He leaves it to God to carry on his own work by Samuel, and sits still, to see how the matter will fall.