If a person appears to be a great saint of Allah and he is walking on water and saying prayers on a ‘sajjadah’ in the air, but if he is performing a single act against the sunnah of the Prophet Muhammad (s) then this person is not a saint of Allah; rather he is a devil.

—Shaykh al-Junaid al-Baghdādī [d. 297 AH]

(Read on pg 101, Dr. Gohar Mushtaq, The Intelligent Heart, The Pure Heart. Ta-Ha Publishers. London: 2006.)