Narrated Abu Wail: 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."

Narrated `Abdur Rahman bin Abza [??]: A man came to `Umar bin Al-Khattab and said, "I became Junub but no water was available." `Ammar bin Yasir said to `Umar, "Do you remember that you and I (became Junub while both of us) were together on a journey and you didn't pray but I rolled myself on the ground and prayed? I informed the Prophet about it and he said, 'It would have been sufficient for you to do like this.' The Prophet then stroked lightly the earth with his hands and then blew off the dust and passed his hands over his face and hands."