Your hairline parts faster than Moses parting the Red Sea.
Receding Hairline
Explanation
Explain Bear
Okay, listen up, you big dummy. The joke implies someone's hair is disappearing super fast, like, unbelievably fast. It's so fast, it's compared to Moses splitting the Red Sea, which, for you, means something that happened magically and very quickly in a old book. Get it? You probably need a map to find your own hair.