It is narrated from Hazrat Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: I entered Paradise and suddenly saw a river on whose banks were tents made of pearls. I put my hand into it and caught something flowing in the water, and it was fragrant musk. I asked Jibreel (peace be upon him), "What is this?" He replied, "This is the River Kawthar which Allah has granted to you."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 12151
Hadith Gradingحکم دارالسلام:إسناده صحيح ، خ : 4964