ʿAlī b. Aḥmad b. Mūsā رضي الله عنه narrated to us, saying that Muḥammad b. Abī ʿAbd Allāh al-Kūfī narrated to him, saying that Abū’l-Khayr Ṣāliḥ b. Abī Ḥammād narrated to him among others, saying: “I wrote to Abī Muḥammad al-Ḥasan b. ʿAlī b. Muḥammad b. ʿAlī b. Mūsā b. Jaʿfar b. Muḥammad b. ʿAlī b. al-Ḥusayn b. ʿAlī b. Abī Ṭālib عليهم السلام—i.e., Imam al-ʿAskarī—asking him about the ritual bath in the nights of the month of Ramaḍān, so he عليه السلام wrote back to me as thus: “If you can perform the ritual bath on the nights of the seventeenth, the nineteenth, the twenty-first, and the twenty-third, respectively, then do that, for in that is the establishment of hope for the Night of Power. If you cannot keep vigil during all of these nights, then do not let the opportunity to revive the twenty-third night escape you. Revive it by performing a hundred units of prayer, and recite in each unit (the chapter of) al-Ḥamd once and the chapter of ﴾Say: “He is Allāh, Who is One”﴿ ten times.”