What Was The Treasure In Aesop's Fable "The Farmer And His Sons"�?

A farmer lay dying. He called his three sons to his bedside and told them, "My sons, there is a great treasure buried on this land, and if you dig deep you will find it." When he died the sons immediately began looking for the treasure. They dug deeply all over the property, but without finding any sign of gold. Where they had dug they planted, and where they had planted they sowed. In time every part of the land was cultivated, and bearing rich harvests of corn, grapes and everything else they needed. In the end there was no land left unexplored, but the sons had become the richest and most successful farmers in the district. It was only then that they realised what the treasure was that their father had promised them; that hard work and honesty would bring them prosperity and happiness. They enjoyed their "treasure" for the rest of their lives.