Imam ar-Redha (a.s) said, ‘To my son Abu Ja’far.’

Muhammad al-Mahmoori narrated from his father as having said, “Once, I was standing near Imam ar-Redha (a.s) in Tooss when one of his companions asked him, ‘If something happens (to you), to whom shall we refer?’ He asked about the next imam after him so that they would know to whom they should obey and submit. Imam ar-Redha (a.s) said, ‘To my son Abu Ja’far.’
Imam al-Jawad (a.s) was yet a child. The man said, ‘I think he is very little as of yet.’
Imam ar-Redha (a.s) replied, ‘Allah sent Jesus the son of Mary (as a prophet) though he was even younger than Abu Ja’far will be when he shall become the imam.’”

The answer of Imam ar-Redha (a.s) was a decisive evidence that Allah the Almighty had chosen Jesus Christ (a.s) as a prophet and given him knowledge while he was still a child and younger in age than Imam al-Jawad (a.s). Prophethood and imamate are from one source, and they are not entrusted to a young or an old man, but rather, they are in the hand of Allah Who chooses for them whom He likes from amongst His people.