In the case of Fada'il ( merits of good deeds) which also includes the habits and traits of the prophet Muhammad peace be upon him, Muhaddithin have unanimously relied upon da'if Ahadith, and have permitted its usage, and rightly so. Otherwise, a great great branch of Deen (faith) would be discarded, and the Ummah would have been deprived of many benefits. The Fuqaha and Muhaddithin themselves have relied upon weak Ahadith to prove several Masa'il (laws), on condition that those weak Ahadith were supported by other chains of transmission.This is due to the fact that Sahih (rigorously authenticated) Ahadith are not always available. It has been the practice of the Hanafi Jurists to give preference to a weak Hadith over personal opinions and deductions. Ibn Hajar Al-Makki Rahimahullah, the author of Al-Khayrat Al-Hisaan has affirmed this fact about the Hanafi school of thought. (Qawa'id Uloom Al-Hadith)
However, we cannot accept narrations that are baseless, or those which have been categorised as fabricated by the temperate among the scholars of Jarah and Ta'dil ( A branch of Hadith, which deals with scrutinising the chain of narrators, and evaluating each narrator, in order to declare him credible or otherwise.)
Imam Nawawi Rahimahullah, the renowned commentator of Sahih Muslim, writes in his book Al-Azkar-:
The scholars amongst the Fuqaha (jurists) and the Muhaddithin have permitted, in fact recommended, the usage of a Da'if hadith, when it pertains to Fada'il (reward and significance of good deeds) or admonition or encouragement for perpetrating evil actions.
Allamah Ibn Al-Humam Rahimahullah, the author of Fath-Al-Qadir writes-:
An action can be categorised as Mustahab if it is substantiated by a Da'if Hadith, but a fabricated Hadith cannot serve this purpose.
Allamah Shabbir Ahmad Uthmani Rahimahullah has na consensus of opinion from the scholars of Hadith regarding the permissibility of utilising Da'if Ahadith for the aforementioned purposes. - Muqaddamah Fath-Al- Mulhim, Page 58.
How can we reject, after the Masters in the field are in harmony regarding the issue? May Allah grant all Muslims the ability to fulfil the rights of Prophet Muhammad peace be upon him, and may He make us fervent adherents of the beloved Sunnah.
(Adapted from 'Shamail-al-Kubra)