Religiousness During The Occultation Of Imam Mahdi (A.S.)
 
The Holy Prophet (S.A.W.S.) said:

"O Ali know that the most strangest of the people of Imaan and the greatest of them in certainty are those people who will be in Aakheruzzamaan (the last period of time). They will not meet the Prophet. And their Imam will be hidden from them. But they will believe (only) due to black upon white."
(Kamaaluddin vol.1 Pg.288)
The "black upon white" means the writings on paper. It means that these people will believe in the Quran and the sunnat as recorded in the books, even though they may not see their Imam (A.S.).
Imam Jafar as-Sadiq (A.S.) said:
"Certainty, the master of this affair has an occupation. Then those who are the pious servants of Allah, will hold firmly to their faith".
(Al Kafi vol.1 Pg.335 and 336, Ghaibat-e-Toosi Pg.455. Ghaibat-e-Nomani Pg.169) 
 
Imam Musa al-Kazim (A.S.) said:
"Blessed are our followers (the shiites) who during the time of occupation (Ghaybah) of the Imam of the Age, identify themselves with our Authority (wilayah) and keep away from our enemies. They belong to us and we belong to them. They have accepted our leadership and we are pleased with their adherence. Therefore, blessed are they. I swear to Allah that they will be with us in our rank in Paradise".
(Kamaaluddin vol.2 Pg.361. Kifayatul Asar Pg.265-266)
 
It is related from Imam Jafar as-Sadiq (A.S.) that the following dua must be recited during the time of ghaibat.

"O Allah ! O Beneficient ! O Merciful ! O the knower of the thoughts (of the hearts) ! make my heart firm upon your religion."
(Kamaaluddin vol.2 Pg.352)