Is it permissible to act upon the least weak and best narrated hadith in a jurisprudential issue for which no marfu’ hadith has been authentically reported, and is this considered an act of giving precedence to a weak hadith over personal opinion?

Some scholars have adopted the view that it is permissible to act upon a weak hadith when no other hadith is found on the matter and it does not contradict stronger fundamental principles. Ibn Badran mentioned that among the principles of Imam Ahmad's madhhab is to act upon mursal (disconnected) and weak hadiths if there is nothing in that chapter to refute them, and he preferred them over qiyas (analogical reasoning). The weak hadith intended here is not the batil (false), munkar (denounced), or one whose narrator is accused, but rather it is considered by him a division among the types of hadith. Thus, if Imam Ahmad did not find anything in that chapter to refute it, such as an athar (narration), a saying of a Companion, or a consensus, then acting upon it was more preferable than qiyas. This principle is generally agreed upon by the imams. As for the virtues of deeds, they have other rulings.