In Jainism, clothing for sadhus varies by tradition:

• Digambara: sadhus practice nudity (they do not wear clothes).
• Śvetāmbar: sadhus wear simple white robes.

For laypeople visiting or offering darśan, dress modestly and respectfully. Wearing underwear is a personal garment and is generally acceptable for a layperson, but it is not part of a sadhu’s attire (especially for Digambaras who are naked). The important point is respect, humility, and not showing arrogance through outside appearance. If you’re unsure, you can follow the local temple’s guidance on dress during darśan or puja.