I have been working to produce a translation and commentary of the fascinating work that is Rijāl al-Kashshī on and off for many years now.
I present a snippet of the translation and commentary of a single report because it has always caught my eye. I believe that it captures the essence of what early Imamism was all about when it came to the law.
Abū al-Ḥasan ʿAlī b. Muḥammad b. Qutayba narrated to me. He said: Al-Faḍl b. Shādhān narrated to me. He said: My father narrated to me from more than one of our fellows from Muḥammad b. Ḥukaym and an associate of his. [Faḍl comments: His name (i.e. the associate) became effaced in the book of my father]. They both (i.e. Muḥammad b. Ḥukaym and his associate) said:
We saw Sharīk standing in a walled-orchard from the orchards of so-and-so [Faḍl: His name also became effaced in the book] so one of us said to the other: "Do you (desire) having a conversation with Sharīk?" So we came to him and greeted him. He returned the greeting.
We said to him: "O Abā ʿAbdillāh (i.e. Sharīk), a question (for you)!"
He said: "In what topic?"
We said: "In ritual prayer"
He said: "Ask whatever occurs to you!"
We said: "We do not want you to say: 'So-and-so said the following, another (authority) said the following.' We want you to chain it back to the Prophet"
He asked: "Is it (i.e. the question) not concerning the ritual prayer?"
We replied: "Yes."
He said: "Ask whatever occurs to you!"
We said: "After what (distance) does shortening the prayer (taqṣīr) become obligatory?"
He replied: "Ibn Masʿūd used to say: 'This sawād (rural agricultural environs) of ours (Kūfa) should not deceive you' but so-and-so used to say: ..."
I (i.e. Muḥammad b. Ḥukaym) interrupted: "We had made an exception that you do not report to us except on the authority of the Prophet!"
He said: "By Allah, it is disgraceful for a shaykh (authority) to be asked a question concerning the ritual prayer and not have anything in it from the Prophet, but even more disgraceful than that would be for me to lie upon the Messenger of Allah!"
We said: "Another question?"
He asked: "Is it not concerning the ritual prayer?
We replied: "Yes."
He said: "Then ask whatever occurs to you!"
We asked: "Upon how many (people) does the Friday prayer become obligatory?"
He said: "The question has returned like a young she-camel (i.e. an idiom which in modern parlance would be 'we are back to square one'). I do not have anything about this from the Messenger of Allah.
We wanted to depart, but he said: "You did not ask this except that you have some knowledge about it!"
I said: "Yes. Muḥammad b. Muslim al-Thaqafī reported to us from Muḥammad b. ʿAlī (al-Bāqir) from his father from his grandfather from the Prophet"
He asked: "Al-Thaqafī the long-bearded one?"
We replied: "Yes."
He remarked: "As for him then he was trustworthy in hadith except that they used to say that he was a khashshābī!"
Then he said: "What did he narrate?"
We said: "He narrated from the Prophet that taqṣīr becomes obligatory after two barīds and that if five men gather including the imām then they are to (pray) the Friday"