The specific part Mr Stewart tweeted is a short speech by a character called Isabella, who has come to plead with Angelo for her brother's life after he is sentenced to die.
Angelo refuses her request, and in response to him she says: 'But man, proud man,
'Dress'd in a little brief authority,
'Most ignorant of what he's most assur'd—
'His glassy essence—like an angry ape
'Plays such fantastic tricks before high heaven
'As makes the angels weep; who, with our spleens,
'Would all themselves laugh mortal'