A good summary of how the classical scholars built their opinions – it is how we should think about Islam too:
“For imam Abū Ḥanīfah Islamic law is like an edifce. Before removing or replacing any of the bricks or making changes to the structure, imam Abū Ḥanīfah will always ask what would this change will have on the structure as a whole. If by removing a single brick the whole building is in jeopardy, imam Abū Ḥanīfah will leave the brick in place keeping in mind the interests of the whole edifice. It was due to his deep understanding of the workings of the shari’ah that the ḥadīth scholar Sulaymān ibn Mahrān al-A’mash (d. 148/765) said to imam Abū Ḥanīfah ‘you (the faqīhs) are the physicians of ḥadīth and we (the muḥaddith) are only pharmacists.’
At the heart of the matter is an attempt to accurately follow the sunna through means which will yield epistemic certainty (yaqīn) as opposed to probable knowledge (ẓann). For imam Abū Ḥanīfah, the principles induced (istiqrā) through a wide range of reading of the Qur’ān and ḥadīth is certain knowledge, whilst the narration of a lone narrator (khabr wāhid), even though it may be ṣaḥīḥ, does not hold the same surety and certainty. Hence in the case of a conflict between the two, the certain is given preference over the probable. Or to put it in another way, the sunna (spirit of the prophetic teaching) is given preference over the ḥadīth (the literal words of the Prophet).
Imam Abū Ḥanīfah rejects the ḥadīth, ‘A Muslim will not be killed in retribution for the murder of a non-Muslim,’ on the basis that it goes against a higher authority with stronger epistemic value i.e. the Qur’ān. His rejection of this otherwise perfectly sound ḥadīth is on the basis that it holds no sanctity for human life which is in contrary to the teachings of the Qurʾān and the established sunna, as Allah, says in the Qur’ān ‘You who believe! Fair retribution is proscribed for you in the case of murder,’ and ‘We prescribed for them in it: a life for a life.’
Imam Abū Ḥanīfah also rejects lone ḥadīth if it goes against an established practice. This established practice is not only connected to the practice of the people of Medina as imam Mālik would want us to believe. On the contrary, every major city had its own established practice. In his response to imam Mālik’s, above mentioned letter, al-Layth ibn Sa’d writes:
When something that the Companions of the Prophet (Sallallahu Alayhi Wasallam) [residing] in Egypt, the Levant and Iraq practiced during the reign of Abū Bakr, ‘Umar andʿ’Uthmān, and they [the Companions] i.e. (this world whilst still practicing this point, they [the caliphs] did not order [the people] to act on the contrary. We do not see it permissible for the Muslim mass to innovate an act upon which their predecessors from the Companions of the Prophet (Sallallahu Alayhi Wasallam) and the Successors did not practice although the Companions of the Prophet differed greatly whilst issuing religious verdicts.
Concerning combining two prayers in one time during heavy rain (which imam Mālik’s teacher Ibn Shihāb az-Zuhrī deemed to be correct), he further writes: The rain in the Levant is much more than the rain in Medina, the extent of which only Allah, knows. However not a single imam from them [i.e. the imams of the Levant] have combined [the prayers] on a rainy night although amongst them were Abū ʿUbayda ibn al-Jarrāḥ, Khālid ibn Walīd, Yazīd ibn Abī Sufyān, ʿAmr ibn al-Āṣ and Muʿādh ibn Jabal. It has reached us that the Prophet said, ‘The most knowledgeable amongst you regarding the lawful and unlawful is Muʿādh ibn Jabal. . . [Also amongst them were] Sharahbīl ibn Ḥasana, Abū’d-Dardāʾ and Bilāl ibn Rabāḥ. In Egypt there were Abū Dharr, Zubayr ibn al-Awwām and Saʿd ibn Abī Waqqāṣ. In Ḥimṣ there were seventy Companions [who fought in the battle of Badr]. In Iraq there were ʿAbd Allah ibn Mas’ūd, Ḥudhayfa ibn al-Yamān and ʿImrān ibn Ḥusayn. The leader of the believers ‘Alī ibn Abī Ṭālib, with whom there were other companions of the Prophet also took up residence there. None ever combined the Maghrib and ʿIshāʾ prayer ever [during heavy rain].
If theʿamal of the people of Medina holds the same level of epistemic value as the mutawātir ḥadīth for imam Mālik, then for imam Abū Ḥanīfah, an action that involve the life of the whole community (umūm balwā) holds similar value. Hence if an action that affects the whole community is only being reported by lone ḥadīths, this ḥadīth immediately comes under suspicion. The reason for this being, if the action being discussed was so prevalent in the community, why is only one person reporting it? An example of this is the ḥadīth concerning rafʿ al-yadayn (the raising of the hands in prayer other than at the beginning) which are all āḥād reports.
Not understanding imam Abū Ḥanīfah’s overall methodology has led some, who have a very superficial knowledge of the inner workings of Islamic law, to maintain that he either did not know any ḥadīth or gives more preference to analogy (qiyās) over ḥadīth. Nothing can be further from the truth.”
[Inhāʾ as-Sakan ilā man Yuṭāliʿ I’lāʾ as-Sunan, Ẓafar Aḥmad ‘Uthmānī Thānawī’]