Sahih Bukhari Volume 002, Book 013, Hadith Number 003.
Narated By Ibn 'Umar : While Umar bin Al-Khattab was standing and delivering the sermon on a Friday, one of the companions of the Prophet, who was one of the foremost Muhajirs (emigrants) came. 'Umar said to him, "What is the time now?" He replied, "I was busy and could not go back to my house till I heard the Adhan. I did not perform more than the ablution." Thereupon 'Umar said to him, "Did you perform only the ablution although you know that Allah's Apostle (p.b.u.h) used to order us to take a bath (on Fridays)?"