How sound is the narration which states that Imam Ja'far al-Sadiq said, while on his deathbed: "The protection of my grandfather, the Messenger of Allah, peace be upon him, is disavowed from me if I disavow Abu Bakr and Umar"?

It is well-known that Ja'far al-Sadiq bore witness to, praised, and showed allegiance to Abu Bakr and Umar, and disavowed anyone who harbored hatred for them. Abu Ja'far Muhammad ibn Ali and Ja'far ibn Muhammad were asked about the two Sheikhs, and they both said: "O Salim, show allegiance to them both and disavow their enemies, for they were two Imams of guidance." Ja'far ibn Muhammad also said: "O Allah, I show allegiance to Abu Bakr and Umar and I love them. O Allah, if there is anything other than this in my heart, then may I not receive the intercession of Muhammad, peace and blessings be upon him, on the Day of Judgment." He also said: "O Salim, would a man revile his grandfather?! Abu Bakr is my grandfather. May I not receive the intercession of Muhammad, peace and blessings be upon him, if I do not show allegiance to them both and disavow their enemies." He also disavowed anyone who claimed to disavow Abu Bakr, and he hoped that Allah would benefit him through his kinship to him.