Zechariah 14:18 says that during the Millennial kingdom if Egypt does
not come to Jerusalem for tabernacles they will have no rain...
    Not only that The whole population of Egypt must come to Jerusalem
for tabernacles... but.. wait for it ...  
   Since Egypt is a type of the World, this prophecy is likely saying
that All the World must come up to Jerusalem each year for tabernacles
as well if they want rain !!!
   In order for them ALL to be able to do this, first the entire
worlds population must be lots smaller to make this possible ..... AND
 that all the worlds population would have to live no more than a
months walk from Jerusalem...  No place in scripture does it say that
each tribe could send representatives to Jerusalem!!! They All had to
go up !!!
   And that God is going to have to  feed this still vast multitude
with manna from heaven...  Its the only way the logistics of all this
can / will work !!!
   Is your brain hurting yet ?  
LewisHB