Sahih Bukhari

Narrated Abu Huraira:While `Umar (bin Al-Khattab) was delivering the Khutba on a Friday, a man entered (the mosque). `Umar asked him, ""What has detained you from the prayer?"" The man said, ""It was only that when I heard the Adhan I performed ablution (for the prayer)."" On that `Umar said, ""Did you not hear the Prophet saying: 'Anyone of you going out for the Jumua prayer should take a bath'?