1 Samuel 19:23

And he went thither to Naioth in Ramah: and the Spirit of God was upon him also, and he went on, and prophesied, until he came to Naioth in Ramah.

Cross-reference

Verse 23 repeats the pattern from verse 20: as the messengers prophesied, so now Saul himself prophesies when the Spirit comes.

In 1 Samuel 10:10, the same Spirit came upon Saul when he first prophesied among prophets — a parallel event in his life.

1 Samuel 10:6 Prophetic fulfillment

1 Samuel 10:6 predicted the Spirit would come on Saul and he would prophesy — this is that pattern repeated.

Numbers 24:2 says 'the Spirit of God came upon him' of Balaam — identical phrasing to Saul's experience here.