The way of life (sira) of the Infallible Imams (A.S.), especially the traditions attributed to them are among the sources employed in the study of Islamic thought history. The most sensitive historical period in the development course of Islamic political thought is the beginning of the Umayyad period and the shift of caliphate to monarchy in this era. In this respect, the Shi‘a Imams (A.S.) took specific measures as their Divine responsibility towards preservation and restoration of Islamic thought. This article studies Imam Sajjad (A.S.)'s assuming position in the most critical period of Islamic history on the basis of his Sahifat al-Sajjadiyya in order to unveil his strategy toward preservation of Shi‘i Imamate line.