Nahj al-Balāgha
Hadith 1567أَمَّا بَعْدُ، فَإِنَّ اللهَ سُبْحَانَهُ بَعَثَ مُحَمَّداً (صلى الله عليه وآله) نَذِيراً لِلْعَالَمِينَ، وَمُهَيْمِناً عَلَى الْمُرْسَلِينَ. فلمَّا مَضى (عليه السلام) تنَازَعَ الْمُسْلِمُونَ الْأَمْرَ مِنْ بَعْدِهِ.
Now, Allāh the Glorified, deputed Muḥammad (may Allāh bless him and his descendants) as a warner for all the worlds and a witness for all the prophets. When the Prophet expired, the Muslims quarreled about power after him.