Sunan Abi Dawud 784
سنن أبي داود#784SahihAnas 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan
Muhammad Muhyi Al-Din Abdul HamidHasan
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim (400)
In-book reference: 2:394