The Jew who became a Muslim in the time of 'Umar b. al-Khattab.
Useful information: The beliefs of the Shi'as who dissociate Allah from forms, bodily traits, and corporealism and maintain the impossibility of seeing Him in this world and in the next. It is generally believed that the traditions which the ahl al-sunna wa'l-Jama'a base their arguments upon are all [the result of] interpolation of Jews in the time of the companions because Ka'b al-Ahbar, the Jew who became a Muslim in the time of 'Umar b. al-Khattab, inserted these beliefs which the Jews maintain, using some naive companions like Abu Hurayra and Wahb b. Munabbih. Most of these are reported in al-Bukhari and Muslim by Abu Hurayra.
It was stated in a previous discussion how Abu Hurayra did not differentiate between the traditions of the Prophet and the traditions of Ka'b al-Ahbar until 'Umar hit and banned him from reporting on the question of the creation of Allah and of the [creation of the] heavens and the earth in seven days.