Patanjali's yoga sutras

You’ll know your practice of fanning the flames of purifying fire is working when, through challenges you face or take willingly, you burn away your ego identity and attain superpowers of the body and spirit, as well as the senses and faculties. 

कायेन्द्रियसिद्धिर् अशुद्धिक्षयात् तपसः ॥ २.४३ ॥

kāyendriyasiddhir aśuddhikṣayāt tapasaḥ || 2.43 ||

kāya—of the physical body, indriya—of the senses, siddhiḥ—the attainment, aśuddhi—of impurity, kṣayāt—owing to the removal. tapasaḥ—through purificatory actions.

When we remove impurities through tapas we obtain siddhihs (super-powers) of the body and the senses. 

Siddhihs (super powers) of the physical body and the sense perceptions occur only after removing impurities through tapas.

Source: ORA: Amanaska (king of all yogas): A Critical Edition and Annotated Translation by Jason Birch

Aśuddhi (अशुद्धि) refers to “impurity”, according to the Bhāṣya (commentary) on the Pātañjalayogaśāstra (i.e., The Yoga Sūtras of Patañjali).—Accordingly: “Yoga is not perfected by one who does not practise Tapas. Impurity (aśuddhi), which is of various kinds because of beginningless Karma, affliction and habitual tendencies and because of which the network of sense objects stands opposed [to Yoga], is not weakened without Tapas. Thus, the mention of Tapas [in the root text]”.