I was in the presence of Imam Al-Ridha عليه السلام that Abi Ja'far Imam Al-Jawad عليه السلام came and he was younger than four years old, he hit his hand on the ground and raised his head towards the sky, thinking, then Al-Ridha عليه السلام said to him ..

"May I be your ransom, why are you thinking for so long?" He عليه السلام replied: "I was thinking about what was done to my mother Fatimah عليها السلام. By Allah! I will take both of them out and I will burn them and then I will spread them and will leave the ashes to the wind."

Imam Al-Ridha عليه السلام called him to himself and kissed his forehead and said: "May my father and mother be your ransom" and then said: "You are the one for it" (meaning Imamate)

Daleel al imamah, p. 207