Show mercy and compassion towards those who have done wrong even if they have already suffered punishment or are repentant for their actions.

This hadith is about the mercy and compassion of Prophet Muhammad ﷺ. It tells us that even when someone has committed a sin or crime, we should still show them mercy and refrain from punishing them if they have already been punished in some other way. In this case, the man was accused of fornication with the slave-girl of Allah's Messenger ﷺ but when 'Ali went to punish him he found that his sexual organ had already been cut off as punishment so he refrained from striking his neck. This teaches us to be merciful even when someone has done wrong because it is possible that they have already suffered enough or are repentant for their actions. We should also remember that only Allah knows what is truly in people’s hearts so we should not judge others too harshly without knowing all the facts first.