question #1 Sahih al-Bukhari 345, Book 7, Hadith 12 : What is the significance of Tayammum in Islamic jurisprudence when water is unavailable for ablution?

Abu Musa 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.”