What made Shylock say, ' A Daniel is come to judgement' ?

One of the great ironies of this play is where Shylock calls Portia, "A Daniel come to judgment, yea, a Daniel!" (4.1.218). Daniel was the biblical judge of Susanna, a woman accused of inchastity by the Elders. The story is famous because Daniel rules in Susanna's favor, thus rescuing her. In addition to freeing her, he then further convicts the Elders. Shylock's mistake is that he is premature in calling Portia a Daniel, because he is the one who represents the Elders, and Antonio signifies Susanna. This inversion comes only a few lines later, when Portia not only frees Antonio, but convicts Shylock of attempted murder.

Shylock said,'A Daniel has come to judgement 'because when potia said a verdict in favour of shylock ,he thought that he would now be able to cut a pound of flesh from antonio's body thus in exclamation he shouted out the above mentioned words.