The story is about a man walking alone on a dark road at night who meets an old man.
The old man gives him one piece of advice: “Keep your heart pure, or the path will turn dark.”
When the man turns around, the old man has vanished — hinting he might have been an angel.
It’s a short, mysterious reminder about keeping the heart clean for guidance in life.
Hence, the moral is: A pure heart leads to light and guidance, while a corrupted heart leads to darkness and being lost.