Sahih Bukhari Volume 8, Book 73, Hadith Number 170.

Narated By Anas bin Malik : The Prophet came to some of his wives among whom there was Um Sulaim, and said, “May Allah be merciful to you, O Anjasha! Drive the camels slowly, as they are carrying glass vessels!” Abu Qalaba said, “The Prophet said a sentence (i.e. the above metaphor) which, had anyone of you said it, you would have admonished him for it”.