Sahih Bukhari Volume 1, Book 7, Hadith Number 341

Narated By Abu Wail : Abu Muisa said to’Abdullah bin Mas’ud, “If one does not find water (for ablution) can he give up the prayer?” Abdullah replied, “If you give the permission to perform Tayammum they will perform Tayammum even if water was available if one of them found it cold.” Abu Musa said, “What about the statement of ‘Ammar to ‘Umar?” ‘Abdullah replied, “Umar was not satisfied by his statement.”