Sahih Muslim Book 003, Hadith Number 0715.
Chapter : Tayammum.
'Aisha reported she had borrowed from Asma' (her sister) a necklace and it was lost. The Messenger of Allah (may peace be upon him) sent men to search for it. As it was the time for prayer, they offered prayer without ablution (as water was not available there). When they came to the Messenger of Allah (may peace be upon him), they made a complaint about it, and the verses pertaining to tayammum were revealed. Upon this Usaid b. Hadair said (to 'Aisha): May Allah grant you a good reward! Never has been there an occasion when you were beset with difficulty and Allah did not make you come out of that and made it an occasion of blessing for the Muslims.