It is reported from Sālim b. Abī Ḥafṣah:

I asked Abū Jaʿfar and his son Jaʿfar (Al-Ṣādiq) about Abū Bakr and ʿUmar, so he replied, “O Sālim, love and ally yourself with them, and dissociate yourself from their enemy, for they were imāms of guidance.” Then he said, “O Sālim, would a man revile his own grandfather? Abū Bakr is a grandfather of mine. May the intercession of Muḥammad ﷺ not reach me on the Day of Resurrection if I do not love and ally myself with them and disassociate from their enemy.”

Al-Dhahabī, Siyar ʾAʿlām Al-Nubalāʾ 6:258.