1 Samuel 9:17
And when Samuel saw Saul, the LORD said unto him, Behold the man whom I spake to thee of! this same shall reign over my people. And when Samuel saw Saul, the LORD said unto him, Behold the man whom I spake to thee of! this same shall reign over my people.
The setting is the gathering of all the elders of Israel to Samuel at Ramah with the complaint that he was old and his sons did not walk in his ways. Their demand was for a king to judge them like all the nations. The injustice connected with the judges was used as a pretext for a change long secretly desired from discontent and pride, even while the integrity and wisdom of Samuel's administration were still acknowledged. Samuel felt the request as a censure upon himself and a direct effort to set him aside. Yet he uttered no reproach but carried the matter to the Lord in prayer and sought counsel from Him alone.
Beforehand God had revealed to Samuel that Saul would come to him and would be chosen to reign over Israel. The disclosure included when the man destined to become king would arrive. When Samuel saw Saul, God identified him as the man appointed to rule over His people.