question #3 Sahih al-Bukhari 337, Book 7, Hadith 4 : What are the conditions under which Tayammum can be performed according to Islamic teachings?

The Prophet (ﷺ) came from the direction of Bir Jamal. A man met him and greeted him. But he did not
return back the greeting till he went to a (mud) wall and wiped his face and hands with its dust
(performed Tayammum) and then returned back the greeting.