(a) Abu Ja'far said: A bowl of liver and hump, that is, camel meat, was brought to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him); he ate it and then did not perform ablution. This narration is munqati' (broken) and mawquf (stopping at the Companion).
(b) Abu Ubaydah said: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) used to eat various kinds of food and did not perform ablution. By the like of this, what is established from the Messenger of Allah (peace and blessings be upon him) is not to be abandoned. The jurists have interpreted the earlier narrations in which ablution is mentioned as referring to cleanliness.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 741