Ibn 'Abbaas Radiyallahu 'Anhu relates:
"Rasulullah Sallallahu 'Alayhi Wasallam once, after relieving himself in the toilet, came out, and was served food. The Sahaabah inquired: 'Will you not perform wudu?'. Rasulullah Saliallahu 'Alayhi Wasallam replied: 'Do I have to perform salaah, that wudu must be performed?'" (TR)
English reference (TR): Book 26, Hadith 177 (TR)
Arabic reference (TR): Book 27, Hadith 186 (TR)