For children, - Spiritual Stories for Children: Tit for Tat!What Goes Around Comes Around, Backfire

It is a law of nature that whatever action we take in this world,
there is always a reaction. If we do well, we stand to gain a good
reward. If we do badly, we should expect a bad outcome ultimately.
"What you sow, so you reap," is a popular saying.
The Noble Qur'an has also guided us on this subject, it says: "If you
do good, you do good to yourselves. Likewise, if you do evil, you do
evil to yourselves." (17:7)
One of the companions of the Prophet Muhammad (SAW)was very fond of
this verse of the Noble Qur'an. He used to recite it loudly and
repeatedly wherever he went.
A Jewish woman who had heard him once wanted to prove him wrong and
thus make him unpopular among his people. She thought up a plot
against him. She prepared some sweets mixed with poison and sent them
to him as a present. When he received them, he went out of the city
taking sweets with him. On the way, he met two men who were returning
home from a long journey. They appeared tired and hungry, so he
thought of doing them a good turn. He offered them the sweets. Of
course, he was not aware that they were secretly mixed with poison. No
sooner had the two travelers taken the sweets, they collapsed and
died.
When the news of their death reached Medina, the city where the
Prophet Muhammad (SAW)resided, the man was arrested. He was brought
in front of the Prophet Muhammad (SAW) and he related what had
actually happened. The Jewish woman, who had mixed poison with the
sweets, was also brought to the court of the Prophet Muhammad (SAW).
She was stunned to see the two dead bodies of the travelers there.
They in fact turned out to be her two sons who had gone away on a
journey.
She admitted her evil intention before the Prophet Muhammad (SAW) and
all the people present. Alas, the poison she had mixed in the sweets
to kill the companion of the Prophet Muhammad (SAW) had instead killed
her own two sons.
What a splendid example of a tragic reaction to a bad action; It shows
how one reaps what he sows. "Do as you would be done by," are the
words of wisdom from the learned and wise men of the past. They teach
us to do well to others in the same way as we like others to do good
to us.