Fortress of the Muslim (Hisn al-Muslim)
حصن المسلم
(64) Chapter: When it rains
(64) الدعاء إذا رأى المطر
Hisn al-Muslim 172 
Allāhumma ṣayyiban nāfi`a. O Allah, (bring) beneficial rain clouds. Reference: Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 2/518.
اللّهُمَّ صَيِّـباً نافِـعاً
Reference : Hisn al-Muslim 172