Narrated Ibn `Abbas:

`Umar asked the people regarding Allah's Statement: 'When comes the Help of Allah (to you O Muhammad against your enemies) and the conquest of Mecca.' (110.1) They replied, "It indicates the future conquest of towns and palaces (by Muslims)." `Umar said, "What do you say about it, O Ibn `Abbas?" I replied, "(This Surat) indicates the termination of the life of Muhammad. Through it he was informed of the nearness of his death."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ، عَنْ سُفْيَانَ، عَنْ حَبِيبِ بْنِ أَبِي ثَابِتٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ عُمَرَ ـ رضى الله عنه ـ سَأَلَهُمْ عَنْ قَوْلِهِ تَعَالَى ‏{‏إِذَا جَاءَ نَصْرُ اللَّهِ وَالْفَتْحُ‏}‏ قَالُوا فَتْحُ الْمَدَائِنِ وَالْقُصُورِ قَالَ مَا تَقُولُ يَا ابْنَ عَبَّاسٍ قَالَ أَجَلٌ أَوْ مَثَلٌ ضُرِبَ لِمُحَمَّدٍ صلى الله عليه وسلم نُعِيَتْ لَهُ نَفْسُهُ‏.‏
USC-MSA web (English) reference : Vol. 6, Book 60, Hadith 493
Arabic reference : Book 65, Hadith 4969