عَنْ أَبِي عُبَيْدَةَ بْنِ عَبْدِ اللَّهِ رَضِيَ اللَّهُ عَنْهُ قَالَ قُلْتُ لِعَائِشَةَ رَضِيَ اللَّهُ عَنْهَا مَا الْكَوْثَرُ قَالَتْ نَهَرٌ أُعْطِيَهُ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فِي بُطْنَانِ الْجَنَّةِ قَالَ قُلْتُ وَمَا بُطْنَانُ الْجَنَّةِ قَالَتْ وَسَطُهَا حَافَّتَاهُ دُرَّةٌ مُجَوَّفَةٌ
Abu Ubaidah bin Abdullah narrates, he says: I asked Sayyida Aisha (may Allah be pleased with her): What is Kawthar? She said: It is a river, which is located in the middle part of Paradise, it has been given to you (peace and blessings be upon him), and on its banks are hollow pearls.