Maliks Muwatta Book 2, Hadith Number 19.
Section : Discontinuing Doing Wudu on Account of Eating Cooked Food.
Yahya related to me from Malik from Zayd Aslam from Ata ibn Yasar from Abdullah Abbas that the Messenger of Allah, may Allah bless him and grant him peace, ate a shoulder of lamb and then prayed without doing wudu.