Yahya related to me from Malik from Abd arRahman ibn al-Qasim from his father that A'isha umm al-muminin said, "We went out on a journey with the Messenger of Allah, may Allah bless him and grant him peace, and, when we came to Bayda' or Dhat al-Jaysh, a necklace of mine broke. The Messenger of Allah, may Allah bless him and grant him peace, stopped to look for it and the people stopped with him. There was no water nearby and the people were not carrying any with them, so they came to Abu Bakr as-Siddiq and said, 'Don't you see what A'isha has done? She has made the Messenger of Allah, may Allah bless him and grant him peace, and the people stop when there is no water nearby and they are not carrying any with them.' " A'isha continued, "Abu Bakr came and the Messenger of Allah, may Allah bless him and grant him peace, had fallen asleep with his head on my thigh . Abu Bakr said, 'You have made the Messenger of Allah, may Allah bless him and grant him peace, and the people stop when there is no water nearby and they are not carrying any with them ' " She continued, "Abu Bakr remonstrated with me and said whatever Allah willed him to say, and began to poke me in the waist. The only thing that stopped me from moving was that the Messenger of Allah, may Allah bless him and grant him peace, had his head on my thigh. The Messenger of Allah, may Allah bless him and grant him peace, slept until morning found him with no water. Allah, the Blessed and Exalted, sent down the ayat of tayammum and so they did tayammum. Usayd ibn Hudayr said, 'This is not the first baraka from you, O family of Abu Bakr.'" A'isha added, "We roused the camel I had been on and found the necklace under it." Malik was asked whether a man who did tayammum for one prayer should do tayammum when the time of the next prayer came or whether the first tayammum was enough. He said, "No, he does tayammum for every prayer, because he has to look for water for every prayer. If he looks for it and does not find it then he does tayammum." Malik was asked whether a man who did tayammum could lead others in prayer if they were in wudu. He said, "I prefer that someone else should lead them. However, I see no harm in it if he does lead them in prayer." Yahya said that Malik said that a man who did tayammum because he could not find any water, and then stood and said the takbir and entered into the prayer, and then someone came with some water, did not stop his prayer but completed it with tayammum and did wudu for future prayers. Yahya said that Malik said, "Whoever rises for prayer and does not find water and so does what Allah has ordered him to do of tayammum has obeyed Allah. Someone who does find water is neither purer than him nor more perfect in prayer, because both have been commanded and each does as Allah has commanded. What Allah has commanded as far as wudu is concerned is for the one who finds water, and tayammum is for the one who does not find water before he enters into the prayer." Malik said that a man who was in a state of major ritual impurity could do tayammum and read his portion of Qur'an and do voluntary prayers as long as he did not find any water. This applied only to circumstances in which it was allowable to pray with tayammum