1 Samuel 10:11
And it came to pass, when all that knew him beforetime saw that, behold, he prophesied among the prophets, then the people said one to another, What is this that is come unto the son of Kish? Is Saul also among the prophets? And it came to pass, when all that knew him beforetime saw that, behold, he prophesied among the prophets, then the people said one to another, What is this that is come unto the son of Kish? Is Saul also among the prophets?
The Spirit of God came upon Saul, enabling him to join the prophets in praising God and to prophesy among them with fluency, wisdom, and earnestness about divine truth. Before this he had been known as an untaught husbandman. Those who had known him beforetime were astonished at the transformation and asked whether he too had become one of the prophets, whether Saul was also among the prophets.
His Spirit-led prophesying was a sign that God had given him another heart and was preparing him for the responsibility of kingship. The episode is evidence that Israel had a school of the prophets where workers were trained. It illustrates how the Spirit's influence among people praising God can move even someone who arrives with a restless, envious, and jealous spirit to join their praise.
The Spirit of God could overrule Saul and cause him to prophesy among the prophets despite his murderous intent toward David. His experience became widely known and, near the end of his reign, gave rise to the saying about Saul being among the prophets.