Call to Prayers (Adhaan)

Bukhari :: Book 1 :: Volume 11 :: Hadith 638

Narrated Abu Sa'id Al-Khudri:

A cloud came and it rained till the roof started leaking and in those days the roof used to be of the branches of date-palms. Iqama was pronounced and I saw Allah's Apostles prostrating in water and mud and even I saw the mark of mud on his forehead.