1. Muḥammad b. Ḥukaym (alive in 183) was among the elite companions of al-Kāẓim who were allowed to debate with other schools of thought. Thus, when the names of those were practising theological disputation were reported to al-Kāẓim he is said to have commented: "As for Ibn al-Ḥukaym then let him be (i.e. he can continue)!" (Rijāl al-Kashshī, n. 843). In another report we read that al-Kāẓim would instruct Muḥammad b. Ḥukaym to sit in the masjid of the Messenger (in Medina) and to debate with "them" until he debated about the status of the ṣāḥib al-qabr (i.e. Abu Bakr who was buried next to the Messenger). (Rijāl al-Kashshī, n. 844). It is not surprising with this background in mind that Muḥammad challenged Sharīk.
2. Sharīk b. ʿAbdallāh al-Nakhaʿī (d. 177) was a very prolific proto-Sunni hadith narrator and was later appointed the judge of Kūfa by the Abbasids. Ibn Mubārak (d. 181) comments that Sharīk was "more knowledgeable of the hadith of his town than (even) Sufyān (i.e. al-Thawrī)"
3. The statement that Sharīk attributes to Ibn Masʿūd in the encounter: "This sawād of ours should not deceive you …" can be independently traced back to Ibn Masʿūd and is found in the Muṣannaf of Ibn Abī Shayba (d. 230).
حدثنا علي بن مسهر عن الشيباني عن قيس بن مسلم عن طارق ابن شهاب عن ابن مسعود قال: لا يغرنكم سوادكم هذا من صلاتكم فإنما هو من مصركم
4. Muḥammad b. Ḥukaym and his associate were sure that Sharīk would not have any Prophetic reports on these secondary issues of the law, in other words the whole thing was a setup to make a point.
This was our Imami predecessors' greatest criticism of proto-Sunni fiqh i.e. it does not have all the answers sourced from the Prophet. In fact, Sunni scholars freely admit that the authentic reports attributed to the Prophet on matters of law number in the few hundreds and all the remaining matters require the faqīh to apply his qiyās (analogical reasoning) or issue a fatwā based on the raʾy (personal opinion) attributed to different companions and their successors.