(a) Abu Dawud (may Allah have mercy on him) said: The mention of Abu Sa'id (may Allah be pleased with him) in this hadith is an error; it is not preserved, rather it is mursal.
(b) The Shaykh (may Allah have mercy on him) said: There is also a third disagreement in it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1096