A turbah (Arabic: تربة‎; Persian: مهر‎ mohr) is a small piece of soil or clay, often a clay tablet, used during salat (Islamic daily prayers) to symbolize earth. The use of a turbah is compulsory in most Shi'a schools of Islam and many Hadith mention the benefits of prostration (Sajda) upon the soil of the earth or an alternative material. The most favoured soil is that of Karbala, the site of the death of Husayn ibn Ali; however, soil from anywhere may be used.