Self-study leads towards the realization of God or communion with one's desired deity.

Verse 2.43

कायेन्द्रियसिद्धिरशुद्धिक्षयात् तपसः ॥४३॥

kāyendriya-siddhir-aśuddhi-kṣayāt tapasaḥ ॥43॥

Self-discipline (tapas) burns away impurities and kindles the sparks of

divinity.

Verse 2.44

स्वाध्यायादिष्टदेवता संप्रयोगः ॥४४॥

svādhyāyād-iṣṭa-devatā saṁprayogaḥ ॥44॥

Self-study leads towards the realization of God or communion with one's desired deity.

Self-discipline destroys all impurities, perfecting the body, mind and senses,

so that consciousness functions freely and attains divinity.

Study of the Self has two paths. One is for communicating from the skin,

through the inner sheaths towards the seer; the other from the seer to the

outer layer of his abode. Though consciousness exists in the body, it needs to be tapped through the practice of asana and pranayama, in which the intelligence acts as a bridge to connect awareness of the body with the core and vice versa. 

This connecting intelligence alone brings harmony of body,

mind and soul, and intimacy with the Supreme Soul (Istadevata).

Traditionally, svadhyaya has been explained as the study of the sacred scriptures and recitation of mantra, preceded by the syllable AUM/om namah shivay / hare Krishna mahamantra , through which the sadhaka gains a vision of his or chosen deity, who fulfils all his desires.

PATANJALI YOGA SUTRAS