Musnad Ahmad 25:95

Sufyan narrated to us, from ‘Amr, from Sa‘id ibn al-Huwayrith, who heard Ibn ‘Abbas say: We were with the Prophet, may Allah bless him and grant him peace, and he went to relieve himself, then he came out. Then he called for food—and he said once: Then food was brought to him. It was said: "O Messenger of Allah, will you not perform ablution?" He said: "I am not about to pray, so that I should perform ablution."