any Shī‘ī Muslims believe al-Khiḍr accompanied the Twelfth Imām, Muhammad al-Mahdi, in meeting one Sheikh Hassan ibn Muthlih Jamkarani, on 22 February 984 CE (17 Ramadan 373 A.H.) and instructing him to build a mosque at that site of their meeting, known as Jamkaran. The site, six kilometres east of Qom, Iran, has been a pilgrimage destination for the Shī‘ah for some time. In the last few years, however, it has become very popular, particularly with young people, and drawn crowds of tens of thousands.

- Wikipedia