When Saul turned around to leave Samuel, God changed his heart, and all the signs came about that day.
1 Samuel 10:9 In-Context
Once these signs are fulfilled, do whatever your hand finds to do, for God is with you.
“Go down ahead of me to Gilgal. I will surely come down to you to sacrifice burnt offerings and fellowship offerings, but you must wait seven days until I come to you and tell you what you are to do.”
As Saul turned to leave Samuel, God changed Saul’s heart, and all these signs were fulfilled that day.
When he 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?”