Matthew 10:23 "But when they persecute you
in this city, flee ye into another; for verily I say
unto you, Ye shall not have gone over the cities
of Israel, till the Son of man be come"

This is an important verse because Jesus jumps
in time to the very end of the age, when the
messengers of the Kingdom would complete the
works of the first apostles.

After 66 A.D. the Gospel preached to Israel all
but ended when the Jewish-Roman wars started.
Israel would be scattered abroad for centuries.

As the ages come to the end, God would gather
them back to their land (did this May, 1948) but still in
unbelief. The task of bringing the message to
them again would have to be done quickly before
the coming of the Son of man.