Twelvers believe that their twelfth Imam, Muhammad al-Mahdi, has been concealed by God, though he remains responsible for the affairs of men and their inward spiritual guidance in his state of occultation (874 CE-present).
[5] While various sects disagree about the identity of the eschatological Mahdi, the belief in him remains popular among all Muslims, possibly owing to numerous traditions to this effect in canonical Sunni and Shia sources.
[11] In Twelver thought, al-Mahdi is also expected to avenge the injustices suffered by Husayn, grandson of the prophet, whose innocent blood is believed to have plunged the Muslim community into a cycle of violence, corruption, and oppression.
[14][3] Non-Twelver sects of Shia have used the term rajʿa to refer to the return of their imams from concealment, including the now-extinct sects of Kaysanite and Waqifite Shia, who denied the deaths of Muhammad ibn al-Hanafiyya (died 700) and Musa al-Kazim (died 799), respectively, and awaited their return.
[14][3] It has been argued that the conceptualization of rajʿa in 8th/9th-century ghulāt texts such as Mā yakūn ʿinda ẓuhūr al-Mahdī ('What Will Happen at the Appearance of the Mahdi') attributed to al-Mufaddal ibn Umar al-Ju'fi (died before 799) has influenced the early 10th-century development of the Twelver Shi'i doctrine on the return of the twelfth and Hidden Imam Muhammad al-Mahdi.
[17] The concept of periodic return of a Manifestation of God is central to prophetology of the Baháʼí Faith, which originated in the 19th century.
This was developed in a milieu of Shiʽa eschatology, initially by Shaykh Ahmad (1753–1826), considered by Baháʼís to be an inspired predecessor to their own faith.