To quote Jaʿfar:
If we were to give fatwā to the people based on our raʾy (opinion) and hawā (desire) we would be among those destroyed. Rather it is athar (reports) from the Messenger of Allah and an aṣl (source) of knowledge which we inherit, son from father, we guard it the way the people guard their gold and silver!
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَامِرٍ عَنْ عَبْدِ اللَّهِ بْنِ مُحَمَّدٍ الْحَجَّالِ عَنْ دَاوُدَ بْنِ أَبِي يَزِيدَ عَنْ الْأَحْوَلِ عَنْ أَبِي عَبْدِ اللَّهِ (ع) قَالَ: سَمِعْتُهُ يَقُولُ: إِنَّا لَوْ كُنَّا نُفْتِي النَّاسَ بِرَأْيِنَا وَهَوَانَا لَكُنَّا مِنَ الْهَالِكِينَ وَلَكِنَّهَا آثَارٌ مِنْ رَسُولِ اللَّهِ (ص) وأصل عِلْمٍ نَتَوَارَثُهَا كَابِرٌ عَنْ كَابِرٍ نَكْنِزُهَا كَمَا يَكْنِزُ النَّاسُ ذَهَبَهُمْ وَفِضَّتَهُمْ
In fact, we know that Muḥammad b. Ḥukaym was particularly proud of this aspect of Imami law. An independent report has him addressing al-Kāẓim as follows:
May I be made your ransom! We have gained understanding of the religion and Allah has made us self-sufficient from needing the people. So much so that a group of us may be in a gathering, not a man asks his fellow a question which comes to his mind except that he receives an answer for it (from your hadith), this is from the mercy of Allah on us through you …
عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ مُحَمَّدِ بْنِ حَكِيمٍ قَالَ: قُلْتُ لابِي الْحَسَنِ مُوسَى عَلَيْهِ السَّلام: جُعِلْتُ فِدَاكَ فُقِّهْنَا فِي الدِّينِ وَأَغْنَانَا الله بِكُمْ عَنِ النَّاسِ حَتَّى إِنَّ الْجَمَاعَةَ مِنَّا لَتَكُونُ فِي الْمَجْلِسِ مَا يَسْأَلُ رَجُلٌ صَاحِبَهُ تَحْضُرُهُ الْمَسْأَلَةُ وَيَحْضُرُهُ جَوَابُهَا فِيمَا مَنَّ الله عَلَيْنَا بِكُمْ ...
6. Muḥammad b. Muslim was an absolute don of Imami hadith. He is quoted as saying that "Nothing crossed his mind except that he asked Abū Jaʿfar al-Bāqir about it". And why not? Muḥammad is said to have resided in Medina for a period of 4 years attending to Abū Jaʿfar almost every single day. Thus it is no exaggeration when he states that he asked al-Bāqir about 30,000 issues and his son Jaʿfar about 16,000 issues.
The 2 issues here would have just been a drop in the oceanic knowledge he possessed and acquired from those two Imams. Muḥammad knew that all the answers he received can be traced back directly to the Prophet without requiring the Imam to state that for each and every instance.