It was related to me from Malik from Musa ibn Uqba from Abd ar-Rahman ibn Yazid al-Ansari that when Anas ibn Malik came back fromIraq, Abu Talha and Ubayy ibn Kab visited him. He brought them somecooked food and they ate, and then Anas got up and did wudu. Abu Talhaand Ubayy ibn Kab asked, "What's this, Anas? Is it an Iraqi custom?"and Anas said, "I wish I had not done it." (i.e. wudu). Abu Talha andUbayy ibn Kab both got up and prayed without doing wudu.
USC-MSA web (English) reference: Book 2, Hadith 27
Arabic reference: Book 2, Hadith 57