It is reported that Imâm Muhammad b. Sîrîn – Allâh have mercy on him – said:

There were people who abandoned knowledge and sitting with the scholars, and [instead] took to their chambers and prayed until their skin dried [from exertion in worship]. Thereafter they began to contradict the Sunnah and thus were destroyed. By Allâh, never does a person act without knowledge, except that he spoils and corrupts more than he fixes and rectifies.

Al-Asbahânî, Al-Targhîb wa Al-Tarhîb 3:98