question #1 Sahih al-Bukhari 348, Book 7, Hadith 15 : What is the significance of Tayammum in Islamic practice when water is unavailable?

Allah’s Messenger (ﷺ) saw a person sitting aloof and not praying with the people. He asked him, “O so and
so! What prevented you from offering the prayer with the people?” He replied, “O Allah’s Messenger (ﷺ)! I
am Junub and there is no water.” The Prophet (ﷺ) said, “Perform Tayammum with clean earth and that
will be sufficient for you.”