מלכים א, פרק כ׳, פסוק מ״א

A disguised figure stands before the king of Israel, maintaining a hidden identity until the moment he finally reveals his face. When the prophet wipes away the ashes that had been covering his eyes, the king recognizes him instantly [רלב״ג].

The king realizes right away that he is speaking with a prophet. This immediate recognition happens simply because this is the exact same prophet who had already approached him in the past. Having met him before, the king easily remembers his face as soon as the disguise is gone [ביאור שטיינזלץ].