Nahj al-Balāgha

Hadith 352
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ومن خطبة له (عليه السلام) تعرف بخطبة الاشباح وهي من جلائل الخُطب (عليه السلام)
This sermon is known as the Sermon of Skeletons [1] (Khuṭbatu ’l-Ashbāḥ) and it holds one of the highest positions among the sermons of Amīr al-mu’minin.
Source: al-Sharīf al-Raḍī