Uttarajjhayana 16.4

16.4

no itthīhiṃ saddhiṃ sannisejjāgae viharittā havai, se niggaṃthe|
taṃ kahamiti ce?
āyariyāha–niggaṃthassa khalu itthīhiṃ saddhiṃ sannisejjāgayassa, baṃbhayārissa baṃbhacere saṃkā vā, kaṃkhā vā, vitigicchā vā samuppajjijjā, bheyaṃ vā labhejjā, ummāyaṃ vā pāuṇijjā, dīhakāliyaṃ vā rogāyaṃkaṃ havejjā, kevalipannattāo vā dhammāo bhaṃsejjā|
tamhā khalu no niggaṃthe itthīhiṃ saddhiṃ sannisejjāgae viharejjā|

A Nirgrantha does not dwell sitting together on the same seat with women.
Why is that?
The ācārya says: If a Nirgrantha practicing celibacy sits together on the same seat with women, there may arise in his celibacy doubt, longing, or uncertainty, or he may suffer a breach, or incur madness, or contract a long-lasting and painful illness, or fall away from the Dharma taught by the omniscient ones.
Therefore, indeed, a Nirgrantha should not dwell sitting together on the same seat with women.