People will first oppose Hazrat Mahdi (pbuh) and then start to gather around him

152- Ghaibat Nomani: It is narrated from Ibne Uqdah from Yahya bin Zakariya bin Shaiban from Yunus bin Kalib from Ibne Bataini from his father from Abu Basir that Imam Ja’far Sadiq (a.s.) said: “The Qaim will not appear until the chain is completed.” I said: “How is the chain completed?” He said: “With ten thousand (fighters), Jibraeel will be on his (the Qaim’s) right and Mikaeel to his left. THEN HE WILL SHAKE THE BANNER AND MOVE. EVERYONE IN THE EAST AND IN THE WEST WILL CURSE THE BANNER. AFTER THAT PEOPLE WILL GATHER AROUND IT ONE BY ONE.

(The Promised Mahdi, Allamah Muhammad Baqir Al-Majlisi, English Translation of Biharul Anwar, Volume 13 (Old Edition)/ Volum 51-52-53 (New Edition), Kitabul Gaibah-Book of Occultation, Imam Mahdi(a.t.f.s)- The Twelfth Imam of the Twelver Shia, Part II, Translator; Sayyid Athar Husain S.H. Rivzi)