Short answer Chovihār/upvās helps the soul by stopping new karmas (saṃvara) and shedding old karmas (nirjarā). By restraining food and water after sunset and fasting with right resolve, attachment to taste reduces, mindfulness grows, and ahimsā is protected.

Key spiritual benefits

• Ahimsā: Not eating/drinking after sunset avoids harming countless night‑active beings; develops compassion.
• Saṃyama (self‑restraint): Control over tongue and senses; weakens rāga–dveṣa (attachment–aversion).
• Saṃvara: Fewer new karmic inflows due to carefulness (apramatta), reduced passions, and fewer bodily activities.
• Nirjarā: Fasting (upvās) is an external austerity (bāhya tapa) that burns previously bound karmas.
• Equanimity: Supports samayik, pratikraman, svādhyāy, and quiet meditation; mind becomes light and steady.
• Aparigraha: Simplicity and contentment increase; dependence on taste and routine comforts decreases.
• Punya: Honest, disciplined fasting with right faith and right conduct yields auspicious merit and inspires others.

To gain these benefits, observe correctly

• Take proper pachkhan (vow/resolve) before starting; keep inner purity, forgiveness, and humility.
• Stop all food and drinks before the day’s sunset; avoid even sips after chovihār begins.
• On upvās days, remain engaged in samayik, pūjā, svādhyāy, pratikraman, and maitri‑bhāva; avoid idle talk and devices.
• Use only properly filtered/boiled water within allowed daytime windows if your tradition permits; otherwise, observe without water as per vow.
• Conclude with kṣamā (seeking forgiveness) and break fast mindfully, without greed.

Notes on traditions

• Both Digambar and Shvetambar traditions uphold chovihār and upvās for ahimsā, saṃvara, and nirjarā. Minor procedural details (exact sunset cut‑off, water permissions/timings) may differ by guru‑paramparā and local maryādā. Follow your Ācārya’s guidance.

Helpful references

• What chovihār means and timing guidance:
• Pachkhan and types of tapas (for right resolve):