What the substance called manna was, is utterly unknown, but,
   from the circumstances in the text, it is evident that it was
   not a natural production, but was miraculously sent by
   Jehovah.  These the learned Abarbinel, a most judicious
   Jewish interpreter, has thus enumerated:  The natural manna
   was never found in the desert where this fell;--where the
   common manna does fall, it is only in the spring time, in
   March and April, whereas this fell throughout all the months
   in the year; the ordinary manna does not melt in the sun, as
   this did (ver. 21);--it does not stink and breed worms, as
   this did, when kept till the morning (ver. 20);--it cannot be
   ground or beaten in a mortar, so as to make cakes, as this
   was;--the common manna is medicinal and purgative, and cannot
   be used for food and nutriment, as this was;--this fell in a
   double proportion on the sixth day, and not on the sabbath,
   as it certainly would have done had it fallen naturally;--it
   followed them in all their journeys, where ever they pitched
   their tents;--and it ceased at the very time of the year when
   the other falls, namely, in March, when the Israelites were
   come to Gilgal.  Whatever this substance was, it does not
   appear to have been common to the wilderness.  From De 8:3,
   16, it is evident that the Israelites never saw it before;
   and from a pot of it being preserved, it is certain that
   nothing of the kind ever appeared again.

  5,16  Le 25:12,22