Sahih Bukhari Volume 5, Book 62, Hadith 3660

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، أَخْبَرَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ أَيُّوبَ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي مُلَيْكَةَ، قَالَ كَتَبَ أَهْلُ الْكُوفَةِ إِلَى ابْنِ الزُّبَيْرِ فِي الْجَدِّ‏.‏ فَقَالَ أَمَّا الَّذِي قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ لَوْ كُنْتُ مُتَّخِذًا مِنْ هَذِهِ الأُمَّةِ خَلِيلاً لاَتَّخَذْتُهُ ‏"‏‏.‏ أَنْزَلَهُ أَبًا يَعْنِي أَبَا بَكْرٍ‏.‏

Narrated By 'Abdullah bin Abi Mulaika : The people of Kufa sent a letter to Ibn Az-Zubair, asking about (the inheritance of) (paternal) grandfather. He replied that the right of the inheritance of (paternal) grandfather is the same as that of father if the father is dead) and added, "Allah's Apostle said, ' If I were to take a Khalil from this nation, I would have taken him (i.e. Abu Bakr)."