It is related in the book, Dala’il al-Imamah of al-Tabari from Zakariyyah b. Adam who says that,
“One day, I was in the presence of Imam ‘Ali al-Ridha when his son, Imam Muhammad al-Jawad, who was less than four years old, was brought to him. When he was brought in, he struck his palms upon the ground and raised his head towards the heavens and remained engrossed in deep thought for a long time.
Seeing this, Imam al-Ridha asked him, ‘May I be your ransom! What are you thinking about?’
Imam al-Jawad replied, ‘I am engrossed in thought regarding the sufferings that befell my mother, Fatimah. By Allah! I will bring out those two men from their graves and burn them and then scatter their ashes into the seas.’
Hearing this, Imam al-Ridha asked his son to be brought closer to him and then he kissed him on his forehead and said, ‘May my parents be your ransom! You are worthy for this affair (Imamat).’”
House of Sorrows Translation of Baytul AhzanShaikh Abbas Al – Qummi