Islam discourages monasticism, which is referred to in the Quran as "an invention".[9][10] However, the term "Sufi" is applied to Muslim mystics who, as a means of achieving union with Allah, adopted ascetic practices including wearing a garment made of coarse wool called "sf".[11] The term "Sufism" comes from "sf" meaning the person, who wears "sf".[12] But in the course of time, Sufi has come to designate all Muslim believers in mystic union.[13]