In Jainism, chaidas (also spelled as "chhedas" or "chhedopasthān"), refers to the rules or codes of conduct that involve the disciplinary regulations for monks and nuns, especially related to expiation and atonement for transgressions. In a broader sense, it also refers to the observance of strict disciplines (vratas) by laypersons and ascetics alike.

The need to follow chaidas arises from core Jain principles:

1. Purification of the Soul (Ātma-shuddhi): Jainism teaches that the soul is bound by karmas due to passions, attachments, and wrong actions. By following the rules of discipline (chaidas), one minimizes new karmic bondage and helps shed existing karma.

1. Self-Restraint (Samyama): Chaidas promotes self-control and discipline, which are essential for spiritual progress. Adhering to these rules helps practitioners stay on the path of right conduct (samyak charitra).

1. Atonement and Correction: If a monk, nun, or layperson commits a transgression, chaidas provides a framework for confession, repentance, and expiation. This ensures that mistakes are acknowledged and corrected, preventing further spiritual downfall.

1. Spiritual Growth: By observing chaidas, one gradually overcomes desires, attachments, and aversions, which are obstacles to liberation (moksha).

1. Community Harmony: Rules and codes maintain order and harmony within the Jain monastic community and society, ensuring mutual respect and the smooth functioning of religious life.

In summary: We need to follow chaidas in Jainism to purify the soul, reduce karmic bondage, practice self-restraint, atone for mistakes, progress spiritually, and maintain harmony within the community. This discipline is a vital part of the Jain path to liberation.