A story tells that two friends were walking through the desert. During some point of the journey they had an argument and one slapped the other on face. The one who got slapped was hurt, but without saying anything he wrote on the sand:
“Today my best friend slapped me on 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 on the mire and started drowning, but the friend saved him. After the friend recovered from near the drowning he wrote on the stone:
"Today my best friend saved my life"
The friend who had slapped and saved his best friends life asked him: "when I hurt you wrote on a stone now when I saved you, you wrote it on stone why?"
The friend replied: "when someone hurt us we should, write it down on sand that the wind of forgiveness can erase it away. But when someone does well for us we should engrave it on a stone that no winds can erase it.