Tayammum (rubbing of hands and face wirh clean earth in absence of water) , and its rulings

 165. ´Aisha narrated: We set out with the Messenger of Allah salla alayhi wa sallam on one of his hourneys until we reached Al-Baida or Dhat-ul-Jaish, when a necklace of mine was broken (and lost). The Messenger of Allah salla alayhi wa sallam stayed there to search for it, and so did the people along with him. There was no water at that place, and they had no water with them, so the people went to Abu Bakr and said: ´´Don´t you see what ´Aisha has done? She delayed the Messenger of Allah salla alayhi wa sallam and the people have no water with them.´´ Abu Bakr, came while the Messenger of Allah salla alayhi wa sallam was sleeping with his head on my thigh, he said to me: ´´Have you head on my thigh, he said to me: ´´Have you detained the Messenger of Allah salla alayhi wa sallam and the people where there is no water, and they have no water with them?´´ ´Aisha said: So he censured me and said what Allah wished him to say, and hit me on my flank with his hand. Nothing prevented me from moving (because of pain) except that the Messenger of Allah salla alayhi wa sallam was on my thigh. The Messenger of Allah salla alayhi wa sallam slept until dawn, and there was no water. So Allah revealed the Divine Verses of Tayammum, and they all performed Tayammum. Usaid bin Hudair who was one of the leaders, said: ´´O the family of Abu Bakr! This is not the first blessing of yours.´´ ´Aisha said: Then we made the camle on which I was riding to stand (from its place) and we found the necklace was beneath it.