Sahih Bukhari Volume 005, Book 057, Hadith Number 117.
Narated By 'Aisha : That she borrowed a necklace from Asma' and it was lost. Allah's Apostle sent some of his companions to look for it. During their journey the time of prayer was due and they prayed without ablution. When they returned to the Prophet they complained about it. So the Divine Verse of Tayammum was revealed. Usaid bin Hudair said (to 'Aisha), "May Allah reward you handsomely. By Allah, whenever you have a difficulty, Allah took you out of it and brought with it, a Blessing for the Muslims."