Abū Hāshim Jaʿfarī said:
[Once] I asked Imām ˊAskarī (pbuh), ‘Your heybat character [usually] prevents me from asking you questions! Do you let me ask you a question, [now]?’
‘Ask’, The Imām (pbuh) replied. I asked, ‘My sir! Do you have any children?’
He replied, ‘Yes!’ I kept on, ‘Where can I meet him, if something will happen to you?’ He stated, ‘In Medina.’
***
Ibn Balāl (One of the very great and trustworthy characters [of that time]) said:
Two years before Imām ˊAskarī (pbuh)’s martyrdom, I received a message from him; wherein, he informed me of his own successor.
Again three days before his martyrdom, he reminded me about his own successor a new message, once more.
[These two sample narrations from the documentary point of view.]
Al- Kāfi, Vol. 1, Ch. 76, Hadith no. 1&2
Dar Intezar- e Ghoghnoos, O. 148