Two friends were walking through the desert.

Two friends were walking through the desert. After a short ride, both of them got into a quarrel and a friend slapped another. The slap that he had eaten, he felt hurt, but did not say anything in the mouth, just put it in sand, "Today my best friend slapped me".
Then they started walking and after a while saw an oasis. They decide where they will rest and take a bath. But the friend who stabbed him started stopping after being stuck in a whistle, another friend saved him. After retrieving he wrote on the stone "Today my best friend saved my life"

Then another friend asked him, "Well, when I slapped you, you wrote on the sand and now write on the stone, why?" He replied, "When someone hits us, it should be written on our sand, The wind can blow it up easily and destroy it. And when someone benefits us, it should be engraved on stone, so that no wind can ever erase it. "