In Jainism, prayaschitta refers to atonement or expiation for transgressions or lapses in conduct, especially for ascetics like Sadhvis (female monks). The Jain monastic code is very strict regarding celibacy (brahmacharya), and even a fleeting thought of sexual nature is considered a lapse.

If a Sadhvi experiences a thought of sex, the mode of prayaschitta would be guided by the rules laid out in texts like the Vyavahara Bhāṣya, Uttarādhyayana Sūtra, and manuals like the Chheda Sūtras. The process typically involves:

1. Alochana (Confession):

The Sadhvi should immediately confess the lapse to her superior (Pravartini or Aryika) or to a learned Sadhvi. Open confession is considered essential in Jain discipline.

1. Prayascitta (Atonement):

Based on the seriousness and intentionality of the thought, the superior may prescribe one or more of the following: - Japa (chanting of mantras): Recitation of sacred Jain mantras or sutras, especially those related to purification and repentance (e.g., Logassa Sutra, Namokar Mantra). - Swadhyaya (scriptural study): Engaging in deep study and reflection on scriptures concerning right conduct and celibacy. - Upavasa (fasting): Observing a fast or partial fast as a means of self-purification. - Kayotsarga (meditation): Practicing kayotsarga (meditative abandonment of the body) and focusing on detachment. - Additional Tapas (austerity): Performing extra austerities as prescribed.

1. Nirveda (Detachment):

Reflecting on the teachings regarding the impermanence of the body and the importance of spiritual purity. Developing deep remorse (pratyakhyana) and resolve (pratyakhyana) not to let such thoughts arise again.

1. Guidance and Monitoring:

The Sadhvi may be kept under the guidance of a senior nun for spiritual counselling and monitoring, as per the Sangha's rules.

References:

• Uttarādhyayana Sūtra, chapters on monk/nun conduct
• Mulācāra (Acharya Vattakera)
• Jain Pratikramana texts

Summary: A Sadhvi who has a sexual thought should perform immediate confession (Alochana), observe the prescribed prayaschitta (chanting, fasting, scriptural study, meditation), reflect deeply to prevent recurrence, and remain under spiritual guidance. This process ensures purification and adherence to the ideal of absolute celibacy in Jain ascetic life.