Ibn Abee Dawoud as Sijistanee said on 34th line of his poem:

“And do not hold the belief of the Khawaarij for indeed
It is only taken by one who desires it, and it is disastrous, shameful.”

Read the explanation of this here:
http://dusunnah.com/wp-content/uploads/2011/05/The-Belief-of-the-Khawaarij-is-Shameful-and-Disastrous.pdf

Note: The full text of the poem is available here: http://islamtees.uk/poetry/#poem1