Matthew 17:13 Meaning

11And Jesus answered and said unto them, Elias truly shall first come, and restore all things.

12But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them.

13Then the disciples understood that he spake unto them of John the Baptist.

14And when they were come to the multitude, there came to him a certain man, kneeling down to him, and saying,

15Lord, have mercy on my son: for he is lunatick, and sore vexed: for ofttimes he falleth into the fire, and oft into the water.