When the Prophet of Allah ﷺ was lifted to the heavens (for travelling) in Paradise, or as he said, a river whose banks were of transparent or hollowed pearls was presented to him. The angel who was with him struck it with his hand and took out musk. Muhammad ﷺ then asked the angel who was with him: What is this? He replied: It is al-Kawthar which Allah has given you.
لَمَّا عُرِجَ بِنَبِيِّ اللَّهِ ﷺ فِي الْجَنَّةِ أَوْ كَمَا قَالَ عُرِضَ لَهُ نَهْرٌ حَافَتَاهُ الْيَاقُوتُ الْمُجَيَّبُ أَوْ قَالَ الْمُجَوَّفُ فَضَرَبَ الْمَلَكُ الَّذِي مَعَهُ يَدَهُ فَاسْتَخْرَجَ مِسْكًا فَقَالَ مُحَمَّدٌ ﷺ لِلْمَلَكِ الَّذِي مَعَهُ مَا هَذَا قَالَ هَذَا الْكَوْثَرُ الَّذِي أَعْطَاكَ اللَّهُ ﷻ