‘Abdullah (b. ‘Umar) reported from his father that while he was addressing the people on Friday (sermon), a person, one of the Companions of the Messenger of Allah (may peace be upon him), entered (the mosque). Umar said to him loudly: What is this hour (for attending the prayer)? He said: I was busy today and I did not return to my house when I heard the call (to Friday prayer), and I did no more but performed ablution only.
Upon this Umar said: just ablution ! You know that the Messenger of Allah (may peace be upon him) commanded (us) to take a bath (on Friday).
Sahih Muslim Book 04, Hadith 1836.