The Quality of Mercy:: The Merchant of Venice contains one of Shakespeare’s most powerful speeches, called “The Quality Of Mercy” – it’s given by Portia, who, disguised as a young, male lawyer, is arguing the case against Shylock.
It is saying that Mercy, like the rain, falls on everyone. No matter what the person is or has done, they are still given mercy. Kings fear it because it doesn't make them better than everyone else and both God and Humans can offer mercy.
Here’s an example of a young girl reciting the speech from memory, as you might hear it in the play: