Once upon a time there were two friends. They 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 my 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 he recovered from the near drowning, he wrote on a stone;

“Today my best friend saved my life.”