Sahih Muslim Book 4, Hadith Number 2013.

Chapter : Endurance in trouble at the fast blow.

Anas b. Malik reported that Allah’s Messenger (may peace be upon him) came to a woman who had been weeping for her (dead) child, and said to her: Fear Allah and show endurance. She (not recognising him) said: You have not been afflicted as I have been. When he (the Holy Prophet) had departed, it was said to her that he was the Messenger of Allah (may peace be upon him), she was mortally shocked. She came to his door and she did not find doorkeepers at his door. She said: Messenger of Allah. I did not recognise you. He said: Endurance is to be shown at first blow, or at the first blow.