كتاب الإيمان
1  
The Book of Faith
(90)
Chapter: The Intercession of the Prophet (saws) for Abu Talib and the reduction of his punishment as a result
(90)
باب شَفَاعَةِ النَّبِيِّ صلى الله عليه وسلم لأَبِي طَالِبٍ وَالتَّخْفِيفِ عَنْهُ بِسَبَبِهِ ‏‏
Sahih Muslim 209 b

Abdullah b. al-Harith reported:

I heard Abbas say: I said: Messenger of Allah, verily Abu Talib defended you and helped you; would it be beneficial for him? He (the Holy Prophet) said: Yes; I found him in the lowest part of the Fire and I brought him to the shallow part.
حَدَّثَنَا ابْنُ أَبِي عُمَرَ، حَدَّثَنَا سُفْيَانُ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ، عَنْ عَبْدِ اللَّهِ بْنِ الْحَارِثِ، قَالَ سَمِعْتُ الْعَبَّاسَ، يَقُولُ قُلْتُ يَا رَسُولَ اللَّهِ إِنَّ أَبَا طَالِبٍ كَانَ يَحُوطُكَ وَيَنْصُرُكَ فَهَلْ نَفَعَهُ ذَلِكَ قَالَ ‏ "‏ نَعَمْ وَجَدْتُهُ فِي غَمَرَاتٍ مِنَ النَّارِ فَأَخْرَجْتُهُ إِلَى ضَحْضَاحٍ ‏"‏ ‏.‏
Reference : Sahih Muslim 209b
In-book reference : Book 1, Hadith 417
USC-MSA web (English) reference : Book 1, Hadith 409
  (deprecated numbering scheme)