Hammad bin Zayd said: Ayyub used to narrate this hadith as marfu' (from the Prophet (peace and blessings be upon him)), then he stopped doing so.
The Shaykh said: Perhaps he stopped only because of a doubt that came to him about its being marfu'. He is Ayyub bin Abi Tamimah al-Sakhtiyani. It has also been narrated from Musa bin Uqbah, Abdullah bin Umar, Hassan bin Atiyyah and Kathir bin Farqad, from Nafi', from Ibn Umar (may Allah be pleased with them both), from the Prophet (peace and blessings be upon him), but its being marfu' is hardly sound except through Ayyub al-Sakhtiyani, and Ayyub too had doubt about it. The narration of the group through sound routes from Nafi', from Ibn Umar (may Allah be pleased with them both), is his own statement, not marfu'. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 19919