Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh))

Bukhari :: Book 6 :: Volume 60 :: Hadith 107

Narrated 'Aisha:

The necklace of Asma' was lost, so the Prophet sent some men to look for it. The time for the prayer became due and they had not performed ablution and could not find water, so they offered the prayer without ablution. Then Allah revealed (the Verse of Tayammum).