During the Minor Occultation (Ghaybat al-Sughrá), it is believed that al-Mahdi maintained contact with his followers via deputies (Arab. an-nuwāb al-arbaʻa or "the Four Leaders"). They represented him and acted as agents between him and his followers. Whenever the believers faced a problem, they would write their concerns and send them to his deputy. The deputy would ascertain his verdict, endorse it with his seal and signature and return it to the relevant parties. The deputies also collected zakat and khums on his behalf.
How did deputies represent al-Mahdi?
acted as agents between him and his followers