I came across this statement by al Nasa'i where he mentions 4 people known to fabricate ahadeeths. Is he referring to Ibn Sa'd al-Baghdadi and number 4? (Muhammad bin Sa'id Syria??
al-Nasa’i (d. 303 A.H.): The liars known for fabricating the Hadith of the Messenger of Allah are four. They are: Arba’ah b. Abi Yahya in Madinah, al-Waqidi in Baghdad, Muqatil b. Sulayman in Khurasan and Muhammad bin Sa’id in Syria.
Ibn Hajr al-‘Asqalani, Tahdhib al-Tahdhib, vol.9 p.366 No.604, Hyderabad, 1326 A.H.cf. Yusuf ‘Abbas Hashmi, Zaynab bint Jahash, ‘Islamic Culture’ vol.XLI, No.1, Hyderabad (India), 1967 < Source