Abu Ubaid (may Allah be pleased with him) said in his book on the unusual words used in some Ahadith that some people passed by a tree that they ate from and they were soon immobilized, just as if a wind had swept through by them and froze them. The Prophet (peace be upon him) said:
"Cool some water in water skins and then pour the water on them between the two Adhans (the Fajr call to the prayer and the Iqamah)."
The Prophet (peace be upon him) mentioned the water skins because they cool the water more than clay containers. He also called the Iqamah an Adhan in this Hadith.
Some doctors stated that the remedy that the Prophet (peace be upon him) prescribed in the Hadith is the one of the most effective against narcolepsy if it occurs in the area of Hijaz, which is a hot dry land.
The inhabitants of that area have a weak instinctive heat. Pouring cold water on the people afflicted by narcolepsy during the above mentioned time, which is the coolest time of the night, will cause the instinctive heat that is scattered throughout the body to be energized an accumulate in the inner parts of the body where the ailment resides.
The powers of the body will then concentrate on expelling and resisting the ailment by Allah's will.
If it were Galinus or Hippocrates who had prescribed this remedy, the doctors would have been amazed by its perfect effectiveness!