It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that he saw the Prophet of Allah (peace and blessings be upon him) eating the meat of a roasted shoulder; then he (peace and blessings be upon him) prayed and did not perform ablution because of it.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10617