 The concept of invisible contagion was eventually widely accepted by Islamic scholars.In the Ayyubid Sultanate, they referred to them as "najasat" ("impure substances").The fiqh scholar Ibn al-Haj al-Abdari (c. 1250–1336), while discussing Islamic diet and hygiene, gave advice and warnings about how contagion can contaminate water, food, and garments, and could spread through the water supply.