What is meant by the "virtues of deeds" for which it is permissible to act upon a weak hadith?

"The merits of deeds" means encouraging or deterring by mentioning a reward or punishment for something that has a firm basis, and it does not include rulings or legislating acts of worship that are not authentically established in the sound Sunnah (definition). It is not permissible to rely on weak hadiths in Islamic law, but it is permissible to narrate them regarding the merits of deeds and for encouragement and deterrence, as long as it is not known that they are false, and provided the act itself is prescribed by a legal proof. It is not permissible to make something obligatory or recommended based on a weak hadith (definition), nor to prohibit something. This is similar to the Isra'iliyyat (stories from Jewish traditions); it is permissible to narrate what is not known to be false among them for encouragement and deterrence, concerning what is known that Allah has commanded or forbidden in our law. However, no scholar would assert a law for us based solely on unproven Isra'iliyyat.