Muslims who practice tawassul point to the Qur'an, Islam's holy book, as the origin of the practice. Many Muslims believe it is a commandment upon them to "draw near" to God. Amongst Sufi and Barelwi Muslims within Sunni Islam, as well as Twelver Shi'a Muslims, it refers to the act of supplicating to God through a prophet, imam or Sufi saint, whether dead or alive. Many Sunni Muslims dispute the practice's usage through the dead.