Sahih Bukhari Volume 5, Book 64, Hadith 4432

حَدَّثَنَا مُحَمَّدُ بْنُ عَرْعَرَةَ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ عُمَرُ بْنُ الْخَطَّابِ ـ رضى الله عنه ـ يُدْنِي ابْنَ عَبَّاسٍ فَقَالَ لَهُ عَبْدُ الرَّحْمَنِ بْنُ عَوْفٍ إِنَّ لَنَا أَبْنَاءً مِثْلَهُ‏.‏ فَقَالَ إِنَّهُ مِنْ حَيْثُ تَعْلَمُ‏.‏ فَسَأَلَ عُمَرُ ابْنَ عَبَّاسٍ عَنْ هَذِهِ الآيَةِ ‏{‏إِذَا جَاءَ نَصْرُ اللَّهِ وَالْفَتْحُ‏}‏ فَقَالَ أَجَلُ رَسُولِ اللَّهِ صلى الله عليه وسلم أَعْلَمَهُ إِيَّاهُ، فَقَالَ مَا أَعْلَمُ مِنْهَا إِلاَّ مَا تَعْلَمُ‏

Narrated By Ibn Abbas : 'Umar bin Al-Khattab used to let Ibn Abbas sit beside him, so 'AbdurRahman bin 'Auf said to 'Umar, "We have sons similar to him." 'Umar replied, "(I respect him) because of his status that you know." 'Umar then asked Ibn 'Abbas about the meaning of this Holy Verse: "When comes the help of Allah and the conquest of Mecca..." (110.1) Ibn 'Abbas replied, "That indicated the death of Allah's Apostle which Allah informed him of." 'Umar said, "I do not understand of it except what you understand."