He owned a pen. He used it to mark his students' books, tick the attendance, draft his meeting minutes, and write something into his diary. One day, he lost the pen. He borrowed it to someone and that someone passed it to another person and so on.
A moment later, he realised that the pen was missing. He tried to track it to the first person who borrowed it. That person said, "Oh, I passed it to another person. Maybe you can ask him."
So, he asked the next person. To his dissappointment, that person also had no clue of the whereabout of the pen as he thought that he had left it somewhere for someone to take it.
He kept on looking. He went around here and there like a cat missing its kittens but to no avail. He went back to the first person who borrowed the pen. That person asked him, "Why are you so gloomy? It is just another pen."
He sighed and looked at his friend.
"Well my friend, it is just another pen. It's not the pen that I am worried about. I am worried about myself."
"Yourself? Why?" His friend looked confused.
"My friend, I am a teacher. A mu'allim."
"So, do I," said his friend.
"My friend, imagine that the pen is one of my students. One day, that student will be passed on to another teacher. He will bring together whatever I've thought him. He will bring along my legacy. However, I have failed to make sure that the student is handed over to the right person and thus I've lost him. I don't know what will happen to him. My friend, I've failed to make sure that I can take care of thing as small as a pen. What is the guarantee that I can take care of something bigger?"
His friend swallowed the thing said by the mu'allim. Eventually, he said, "Indeed, my friend. It is a lost for both you and I. It is OUR lost."