Fortress of the Muslim (Hisn al-Muslim)
حصن المسلم
(20) Chapter: Between the two prostrations
(20) دعاء الجلسة بين السجدتين
Hisn al-Muslim 48 
Rabbi’ghfir lī, Rabbi’ghfir lī. Lord, forgive me. My Lord, forgive me. Reference: Abu Dawud 1/231. See also Al-Albani, Sahihibn Mdjah 1/148.
رَبِّ اغْفِـرْ لي ، رَبِّ اغْفِـرْ لي
Reference : Hisn al-Muslim 48