Abdullah bin Ahmad bin Hanbal (may Allah have mercy on him) heard his father say: There is a shaykh, Mubashshir bin Ubayd, who lived in Hims; I think he was from Kufah. Baqiyyah and Abu al-Mughirah narrated from him. His hadiths are fabricated and false. Imam al-Bukhari (may Allah have mercy on him) called Mubashshir bin Ubayd munkar al-hadith (one whose narrations are rejected).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12653