Narrated Abu Bishr:

Sa`id bin Jubair said that Ibn `Abbas said about Al-Kauthar. "That is the good which Allah has bestowed upon His Messenger." I said to Sa`id bin Jubair. "But the people claim that it is a river in Paradise." Sa`id said, "The river in Paradise is part of the good which Allah has bestowed on His Messenger."

حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هُشَيْمٌ، حَدَّثَنَا أَبُو بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ أَنَّهُ قَالَ فِي الْكَوْثَرِ هُوَ الْخَيْرُ الَّذِي أَعْطَاهُ اللَّهُ إِيَّاهُ‏.‏ قَالَ أَبُو بِشْرٍ قُلْتُ لِسَعِيدِ بْنِ جُبَيْرٍ فَإِنَّ النَّاسَ يَزْعُمُونَ أَنَّهُ نَهَرٌ فِي الْجَنَّةِ‏.‏ فَقَالَ سَعِيدٌ النَّهَرُ الَّذِي فِي الْجَنَّةِ مِنَ الْخَيْرِ الَّذِي أَعْطَاهُ اللَّهُ إِيَّاهُ‏.‏