Grounds for accepting the caliphate and the qualities of a ruler
Nahj al-Balāgha|Volume 1|Book 1|Chapter 131
اللَّهُمْ إِنّي أَوَّلُ مَنْ أَنابَ، وَسَمِعَ وَأَجَابَ، لَمْ يَسْبِقْنِي إِلاَّ رَسُولُ اللهِ (صلى الله عليه وآله) بِالصَّلاَةِ.
O my Allāh! I am the first who leaned (towards Thee) and who heard and responded (to the call of Islam). No one preceded me in prayer (ṣalāt) except the Prophet.