Was the Prophet (peace be upon him) cautious of germs and did he use soap or lotus fibers, and should we follow modern methods of germ prevention or suffice with water, and does using potash instead of modern soap bring greater reward by following his Sunnah?

Islamic Sharia is flexible, and the default rule regarding customs is permissibility and clemency unless they contradict a religious text. Therefore, there is no objection to using modern inventions such as body and clothing cleansers. A Muslim is not required to revert to old cleansers like sidr and ushnan unless modern means are unavailable, as the objective is cleanliness and preservation of health.

Furthermore, Sharia encourages cleanliness and made ablution a condition for the validity of prayer. The use of sidr in some ritual baths was for enhanced cleaning, not as an act of worship.

Regarding clothing, a Muslim is required not to exceed what is necessary; exceeding what suffices is considered blameworthy extravagance in Sharia. Moderation in eating, drinking, and clothing is what is required.