“Atham” is said in two ways in Jain tradition. Please follow the one you meant:
1) Attham (three‑day fast)
- Meaning: Complete fast for 3 continuous days; parna (break) on the morning of the 4th day.
- Water rule:
- Shwetambar: usually only boiled water, in daytime (sunrise to sunset).
- Digambar: generally stricter; some take very limited boiled water in daytime; a few observe nirjal as per capacity.
- How to do it (simple steps):
- Before starting (Day 0)
- Do Navkār Mantra, samayik, and take pachchakkhan (pratyākhyān) for 3‑day upvās.
- Decide water‑niyam clearly (e.g., “boiled water only in daytime”).
- During the fast (Days 1–3)
- No food. Keep maun/mit‑bhāshā (silence/minimum speech), avoid travel and screens if possible.
- Daily samayik, pratikraman, svādhyāy, Navkār‑jāp, and kshamā‑bhāvanā.
- Drink only as per your vow and maryādā; never after sunset.
- Parna (Day 4 morning, within parna‑kāl)
- Begin with a few sips of lukewarm boiled water.
- Take very light food (pej/kanji, thin moong broth, soft plain khichdi).
- Do gratitude and a fresh small pachchakkhan for careful conduct.
- Upvās pachchakkhan and parna basics:
- Notes on Attham meaning and practice:
2) Ātham/Āṭhām (Upvās on the 8th lunar day, Ashtamī)
- Meaning: A one‑day upvās specially done on the 8th tithi.
- How to do it:
- Take pachchakkhan in the morning for upvās on Ashtamī.
- Through the day: no food; only boiled water in daytime as per maryādā (Shwetambar/Digambar note as above).
- Do chaityavandan, samayik, pratikraman, svādhyāy; keep apramattata (alert non‑violence) in movement.
- Next morning, do parna within the proper parna‑kāl, starting gently with boiled water and light food.
- Fasting rules and water timing guidance:
(water‑niyam principles apply similarly to one‑day upvās)
Important maryādā (both cases)
- Always follow your sect’s rules:
- Shwetambar: boiled water only in daytime; strict parna‑kāl.
- Digambar: generally more austere; observe stricter water discipline and day‑time only parna.
- Health care: If unwell, choose a lighter niyam (ekāsan/biyāsan/pānahār upvās) rather than forcing. Guidance:
- Spirit over number: Aim at kashāya‑kṣaya (reducing anger, pride, deceit, greed), maitri and samata.
If you specifically meant the 8‑day fast (Atthāī), see: