Anas b. Malik said:The Messenger of Allah (ﷺ) said: A surah has just been revealed to me. He then recited:”In the name of Allah, the Compassionate, the Merciful. Lo! We have given thee Abundance” until he finished it. Then he asked: Do you know what Abundance (al-Kawthar) is? They replied: Allah and His Apostle know it better. He said: It is a river of which my Lord, the Exalted, the Majestic has promised me to give in Paradise

English translation · Sunan Abu Dawud