The Farmer and His Sons By Aesop’s Fables

No Moral. Suggest us a moral of this fable in comment section.
A father, being on the point of death, wished to be sure that his sons would give the same attention to his farm as he himself had given it. He called them to his bedside and said, “My sons, there is a great treasure hid in one of my vineyards.” The sons, after his death, took their spades and mattocks and carefully dug over every portion of their land. They found no treasure, but the vines repaid their labour by an extraordinary and superabundant crop.