Hazrat Mahdi's (as) followers will be made up of those believers from whom Allah takes a monument in Qalu Bala

Ali ibn Abu Hamza says: Imam Abu Abdullah Jaffar Sadik said: “When the Qaim [Hazrat Mahdi (as)] appears, most people will deny him. Because he will appear as a young major. ONLY THOSE BELIEVERS FROM WHOM ALLAH TAKES AN OATH IN THE WORLD OF SOULS WILL BELIEVE IN HIM.” (Sheikh Muhammad ibn Ibrahim Numani, al-Ghaybah al-Numani, p. 247)