the inhabitants both of the east and of the west, is always meant spring water, in opposition to dead, stagnant water contained in ponds, pools, tanks, or cisterns; and what our Lord means by it is evidently the Holy Spirit, as may be seen, John 7:38, John 7:39.
As water quenches the thirst,
refreshes and invigorates the body,
purifies things defiled,
and renders the earth fruitful,
so it is an apt
emblem of the gift of the Holy Ghost, which so satisfies the souls that
receive it that they thirst no more for earthly good: it purifies also
from all spiritual defilement, on which account it is emphatically
styled the Holy Spirit; and it makes those who receive it fruitful in
every good word and work."
Adam Clarke