It is reported that Imām Muḥammad b. Sīrīn – Allāh 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 Allāh, never does a person act without knowledge, except that he spoils and corrupts more than he fixes and rectifies.
Al-Aṣbahānī, Al-Targhīb wa Al-Tarhīb 3:98