Mukhtasar Bukhari (Abridged) 157 — Evidence for not performing

It is narrated from Sayyiduna Amr bin Umayyah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, ate a shoulder of a goat, then he was called for prayer. So he, peace and blessings be upon him, put down the knife. After that, he, peace and blessings be upon him, performed the prayer and did not perform ablution (again).