Albert Barnes Commentary 1 Samuel 14:10

"But if they say thus, Come up unto us; then we will go up; for Jehovah hath delivered them into our hand: and this shall be the sign unto us." — 1 Samuel 14:10 (ASV)

Although it is not explicitly stated that the Spirit of the Lord came upon him—as it is in the cases of Gideon (Judges 6:34), Othniel (Judges 3:10), and others—the entire narrative, especially 1 Samuel 14:13–16, indicates an extraordinary divine intervention.