In Jainism, when people say “Attham / Aatham tapasya fasting”, they usually mean this:

1. Meaning of Attham Tap (3‑day fast)

• Attham (or Aatham tap) = continuous 3‑day fast (about 72 hours).
• You do not eat any food at all for 3 full days.
• On the 4th morning, you do pārṇā (break the fast) in a proper, gentle way.

Both Shwetambar and Digambar traditions accept this meaning. The main difference is usually about water rules:

• Shwetambar:

- No food for 3 days. - Generally only boiled, filtered water in daytime (sunrise to sunset), as per your niyam. - No water after sunset.

• Digambar:

- Many do it as nirjal (no water) or with very little boiled water in daytime only, as guided by ācārya / guru.

2. Simple way it is done

Before starting (Day 0)

• Take pachchakkhan (vow) for 3‑day upvās.
• Do Navkar Mantra, small samayik or prārthanā.
• Decide your water rule clearly.

During the 3 days (Days 1–3)

• No food at all.
• Water only as per niyam and only in daytime.
• Do:

- Navkar jāp - Samayik / pratikraman - Svādhyāy (scripture reading/listening) - Kṣamā‑bhāvanā (forgiveness feeling)

• Speak less, avoid anger, arguments, and heavy work.

Pārṇā (Day 4 morning)

• Within proper pārṇā‑kāl (as per local maryādā).
• Start with a few sips of warm boiled water.
• Then take very light food (pej, thin khichdi, light dal, etc.), in small quantity.
• Do prārthanā and thank Bhagwān; ask forgiveness for any faults in your tap.

3. Spiritual purpose

• Attham is a form of tapa (austerity) to:

- Stop new karma (samvar) - Shed old karma (nirjarā) - Soften anger, pride, deceit, greed.

• The numbers (3 days) are secondary; more important is:

- Humility - Non‑violence - Control over mind, speech, and body - Focus on dharma (svādhyāy, pratikraman, Navkar).

You can read a very simple explanation of Attham tap here: