The samaritans called him the saviour of the world because of the woman who testified.The woman told them that Jesus told her everything she did.

The harvest is all those people who were converted through the words that were preached to them(i.e all  those sinners who dicided to give thier lives to the lord).

It is sowed by the all mighty God and spread to the world through his servants.

The ones who reap it are those people on earth who get the word through God's servants.