Theory:

     Now the governors of other provinces grew terribly jealous of him and began to talk to the king against him. They said, β€œHe is very dishonest, and keeps for himself part of the money that he collects as tax from the people.” Why did he always carry with him, they added, an iron chest? Perhaps he carried in it the treasure that he had secretly collected. After all, they said mockingly, he was an ordinary shepherd and could behave no better.
Explanation:
 
When the fame of the humble and wise shepherd had spread among the people of the country, it affected the governors of other provinces in a negative way. The governors belonging to other provinces had grown jealous of the shepherd's fame. They started to talk badly about the poor, honest shepherd behind him. The other governors even questioned his honesty. They accused him of saving money for himself, stealing from the tax he collects from the people. The governors pointed out an iron chest he usually carries with him always. They blamed him for having for carrying the iron chest all the time, as, it helps him to hide the treasure collected.

The governors made fun of the shepherd, and adding to the above statements, pointed out that his profession as a shepherd was responsible for his behaviour. They said a shepherd couldn't be expected to behave in a better way.
 
Meaning of difficult words:
  
S.No
Words
Meaning
1.
Jealous
Feeling sad or angry about what someone has
2.
Accused
To say that somebody has done something wrong
3.
Hide
Keep something in a place so that it cannot be found
4.
Blame
To say somebody or something is responsible for a bad thing happened
5.
Treasure
A collection of valuable things like gold, silver etc.
6.
Mocking
To make fun of someone or something
Reference:
National Council of Educational Research and Training (2006). The Shepherd's Treasure (pp. 07-10). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.