A turbah, or mohr, also known as khāk-e shefā, sejde gāh or prayer stone, is a small piece of soil or clay, often a clay tablet, used during salah to symbolize Earth. The use of a turbah is recommended according to the Twelver branch of Shia Islam, a unique practice of the sect, and many ahadith mention the benefits of prostration upon soil or an alternative natural material. The most recommended soil is that of Karbala, the site of the martyrdom of Husayn ibn Ali; however, soil from anywhere may be used. In the absence of soil, plants or items made from these may be substituted. This provision has been extended to include paper.