What was revealed to the Prophet (saw) when men were unable to perform ablution and offer their prayers due to the lost necklace of Asma´?
 Narrated `Aisha:                     The necklace of Asma' was lost, so the Prophet sent some men to look for it. The time for the prayer became due and they had not performed ablution and could not find water, so they offered the prayer without ablution. Then Allah revealed (the Verse of Tayammum).