Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 6066
Anas b. Malik reported that Allah's Apostle (may peace be upon him) told me something secretly. I informed none about that and Umm Sulaim asked me about it, but I did not tell her even.