A story of Two friends walking in a dessert

A story tells that two friends were walking through
the desert.
.
During some point of the journey they had an
argument, and one friend
slapped the other one in the face. The one who got
slapped was hurt, but without saying anything,
wrote in the sand: “TODAY MY BEST FRIEND
SLAPPED ME IN THE FACE.”
.
They kept on walking until they found an oasis,
where they decided to take a bath.
.
The one, who had been slapped, got stuck in the
mire and started drowning, but the friend saved
him.
After the friend recovered from the near drowning,
he wrote on a stone: “TODAY MY BEST FRIEND
SAVED MY LIFE."
.
The friend who had slapped and saved his best
friend asked him, “After I hurt you, you wrote in the
sand and now, you write on a stone,
why?”
.
The other friend replied:
“When someone hurts us, we should write it down
in sand where winds of forgiveness can erase it
away. But, when someone does something good
for us, we must engrave it in stone where no wind
can ever erase it.”