Sahih Muslim Book 30, Hadith Number 5706.

Chapter : The cistern of our Apostle (may peace be upon him) and its characteristics.

Anas b. Malik reported Allah’s Apostle (may peace be upon him) as saying: Some persons from amongst my associates would turn to my Cistern; when I would see them and they would be presented to me, they would be detained in the way while coming to me. I would say: My Lord, they are my companions, they are my companions, and it would be said to me: You don’t know what innovations they made after you.