If you mean “Why do Jains not eat after sunset?” — the practice is called Chovihar (Chauvihar).

• Ahimsa (non‑violence): After sunset, tiny living beings (insects, microorganisms) become harder to see and are more active. Cooking/eating then can harm them. Avoiding food and water after sunset reduces this unseen himsa.
• Carefulness (samiti) and discipline (sanyam): It trains self‑control, simplicity, and a steady daily routine devoted to prayer, study, and Pratikraman at night.
• Purity and health: Daylight meals are easier to inspect and digest; night eating is avoided to keep the body and mind light for sadhana.

How it’s observed

• Chovihar: No food or water after sunset until sunrise.
• Tivihar: Food stops before sunset; after sunset even water is avoided (some use the terms interchangeably in regions).
• Monks and nuns follow this very strictly; many householders take a pachchakkhan (vow) daily to observe it.

Tradition notes

• Shvetambar and Digambar both uphold not eating after sunset as part of ahimsa and discipline. The exact rules a householder follows (Chovihar vs. Tivihar, medical exceptions, etc.) are taught by one’s tradition and teacher, but the principle is the same: protect life and cultivate restraint.

For a simple overview and pachchakkhan details: