The well-known sunnah (al-sunnah al-mashhūra, Arabic: السنة المشهورة) continues to be used till today by Hanafi scholars to:
- establish rulings of the Hanafi jurisprudence,
- do tafsir of the Qur'an,
- decide on which Qur'an verses are abrogated
- introduce specificity (mukhaṣṣaṣ, Arabic: مخصص) to what is apparently generalized (mu'ammam, Arabic: معمم)
- disqualify deductive analogy (qiyās, Arabic: قياس), and
- arbitrate between single-chain (aḥād, Arabic: الآحاد) hadiths.
However, the Hanafi scholars have their reasons for doing so till today, and they have an established methodology that they follow. Moreover, the definitions of well-known (mashhūr, Arabic: مشهور) hadith in jurisprudence does not bear the same definition as in hadith terminology. Mashhūr hadiths in jurisprudence rely on acceptance and application by the companions and the generation after, which in terms of Hanafi jurisprudence equates to a mutawātir hadith. Accordingly, advancement in archiving and retrieval of hadith books and their availability in modern days is not a factor.
The detailed answer is below.
Definitions
Hadith terminology
The science of hadith has a terminology system that defines the acceptability of a hadith in terms of attribution for elevated to the Prophet ﷺ (marfū', Arabic: مرفوع) or terminated at a companion (mawqūf, Arabic: موقوف) hadith.
According to Ibn al-Salah, for a hadith to be authentic, five conditions have to be met; three of which are affirmations, and two are negations: the narration chain (sanad, Arabic: سند) has to be complete and continuous from its start till its termination, with each narrator being upright and trustworthy ('adl, Arabic: عدل) who demonstrates accurate and sound memory (tāmm al-dabt, Arabic: تام الضبط), with no anomaly (shudhūdh, Arabic: شذوذ) nor defect ('illa, Arabic: عله).
Sound hadith fall into the categories (in terms of the numbers of companions in the narration chain) into well-known (mashhūr, Arabic: مشهور), in which the narration chain has three more companions in the first layer; or rare (gharīb, Arabic: غريب) in which the narration chain has only one companion in the first layer; and in between ['azīz (Arabic: عزيز)].
Hanafi jurisprudence
Hanafi scholars, in addition to the narration and its acceptance, added application and its adoptance. They split hadiths into three categories: successive (mutawātir, Arabic: متواتر), well-known (mashhūr, Arabic: مشهور), and singular (ahād, Arabic: آحاد) hadiths.
As for mutawātir and ahād hadiths, there is a clear agreement between scholars of hadith and jurisprudence. When it comes to mashhūr hadiths, Sharaf al-Dīn al-Rahāwi said in the footnotes of his book Hāshiyat al-Rahāwi 'ala Sharh al-Manār (Arabic: حاشية الرهاوي على شرح المنار), Al-Matab'a al-'Utmaniyya, 1315 AH, pp. 619, that the use of the word mashhūr is not what is classified by scholars of hadith as having three or more narrators, but rather on the acceptance of its applicability by the companions and the following generation, and the extension of its practice among them.
In Al-Fusūl fi al-Usūl (Arabic: الفصول في الأصول) by Abu Bakr al-Rāzi al-Jassās, vol. 2, pp. 68, he said that an ahād hadith, when accepted and practiced by consensus (ijmā', Arabic: اجماع) of the companions, elevates that hadith in terms of jurisprudence to that of a mutawātir hadith.
Justification of using well-known sunnah
According to Hanafi scholars, even major narrators erred or forgot at one stage. While it is accepted from a hadith scholarly perspective that a trusted narrator would be trusted on all hadiths, when it comes to jurisprudence, trustworthiness has an added element: acceptability and adoption in terms of practice.
To fortify their view, Hanafi scholars quote:
Ahmad ibn Hanbal said about Yahya al-Qattān: "I saw no one less wrong than Yahya ibn Sa'īd, and he erred in hadiths," then he added: "And who is above error and being corrected."
In Al-'Ilall al-Sughra, vol. 6, pp. 240, Al-Tirmidhi said: "No major imam escaped without an error or lapse of memory, in spite of their memorization."
Other major scholars (Muslim ibn al-Hajjaj, Ibn Rajab, Al-Dhahabi, etc.) all have similar sayings.
To overcome the problem of potential error on the part of a trusted narrator, priority was given to hadiths that were known to have been accepted in terms of adoption by the companions and the generation after. The rationale is if those two generations practiced an ahād hadith, the hadith may be considered as mutawātir in terms of application albeit it is ahād in terms of narration. This is what is termed as well-known or mashhūr sunnah.
In other words, authenticity is elevated through either practice or narration.
Methodology of application of well-known sunnah
Here, we can look at some examples to see how Hanafi scholars applied their concept of well-known sunnah.
One well-established judicial rule is that the burden of the proof lies on the one making the claim, and whoever denies has to do so under oath. According to Al-Jassās, this rule relies on an ahād hadith that is well accepted, adopted, and practiced by the Islamic nation, which elevates its stance as a hadith:
عَنِ ابْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا; أَنَّ اَلنَّبِيَّ ﷺ قَالَ: لَوْ يُعْطَى اَلنَّاسُ بِدَعْوَاهُمْ لَادَّعَى نَاسٌ دِمَاءَ رِجَالٍ وَأَمْوَالَهُمْ وَلَكِنِ اَلْيَمِينُ عَلَى اَلْمُدَّعَى عَلَيْهِ. وَلِلْبَيْهَقِيِّ بِإِسْنَادٍ صَحِيحٍ: اَلْبَيِّنَةُ عَلَى اَلْمُدَّعِي, وَالْيَمِينُ عَلَى مَنْ أَنْكَرَ
Narrated Ibn 'Abbas (RA): The Prophet (ﷺ) said: "If people were given whatever they claimed (in disputes), some people would claim the lives and wealth of others; but the oath (of denial) must be taken by the defendant." [Agreed upon]. al-Baihaqi has reported with a Sahih (authentic) chain of narrators: "But the proof (Bayyinah) lies on the one who is making the claim, and the other (Yamin) must be taken by the one who rejects the claim."
— Bulugh al-Maram 1423
They consider this hadith to take precedence as a well-known sunnah over a similar ahād hadith in Jami` at-Tirmidhi 1343 that the Prophet ﷺ passed judgement based on an oath along with a single witness.
Another example is related to the permissibility of a Muslim's blood (see Sunan an-Nasa'i 4057) in three cases only (married committing adultery, intentional murder, and apostasy), versus another hadith of killing someone who is caught four times drinking alcohol (see Sunan Abi Dawud 3680) as the Prophet ﷺ did not come across a situation to put into practice the latter.
A third example is the Sahih al-Bukhari 6764 hadith about a Muslim not inheriting a disbeliever, and a disbeliever not inheriting a Muslim. This hadith is narrated only through Usāma ibn Zaid, but it is elevated to the level of mutawātir due to its wide application during the time of the Prophet ﷺ.
Conclusion
The Hanafi scholars addressed errors or forgetfulness of trustworthy narrators through adding another dimension to the narration, which is the acceptance and adoption of companions and the generation after in terms of adoptance, which defines the well-known sunnah, even from hadiths that ahād.
References
This answer is largely based on the research done by Salah Mohammad Salem Abu al-Hajj, PhD, who is the Dean of Hanafi jurisprudence at the World Islamic Sciences and Education University in Jordan.
Salah Mohammad Salem Abu al-Hajj. The Well-Known Sunnah According to the Hanafis and its Application in Their Books. World Islamic Sciences and Education University, 2010.
Salah Mohammad Salem Abu al-Hajj. Sabīl al-Wuṣūl ela 'Ilm al-Uṣūl (Arabic: سبيل الوصول إلى علم الأصول). Amman, Jordan: First Ed. Dar al-Furquan, 2006.
Dar Al-Ifta. "Classification of the Sunnah in terms of how it reached us." (Arabic: تقسيم السنة من حيث وصولها إلينا). Islamic Research Magazine. Accessed June 27, 2017. URL.
Ibn al-Salah al-Sharazuri. An Introduction to the Science of the Hadith. United Kingdom: Garnét Publishing, 2006.