Is it permitted to use weak Hadith for matters of Nafl?

Quran

Hadith

Islamic Text

Yes. 

Weak Hadith cannot be used for the fundamentals of creed (Aqeedah) or legal rulings but can be used for less significant issues. Such issues include Nafl (supererogatory) actions, virtues of the pious (Manaqib), encouraging good deeds (Targheeb) and other matters too. 

ويَجُوزُ رِوَايَةُ ما عدا الموضُوعَ في بَابِ التَّرْغِيبِ والتَّرْهِيبِ والقَصَصِ والمواعِظِ ونحوِ ذَلِكَ إلا في صِفاتِ اللهِ -عَزَّ وجَلَّ-، وفي بابِ الحَلالِ والحرَامِ. (الباعث الحثيث شرح اختصار علوم الحديث)

It is permitted to narrate anything that is not fabricated when it relates to encouraging (good deeds) and discouraging (sins), stories, reminders, and the like. However, it is not permitted (to use such narrations) regarding the attributes of Allah (Most High) or Halal and Haram (i.e. legal rulings). (Imam Ibn Katheer, al-Baith al-Hatheeth). 

Although Imam Ibn Katheer did not exclude very weak Hadith, they have been excluded elsewhere. See ‘Using weak Hadith’ for references. 

In the Muqadimah of Imam Ibn Salah we see additional areas in which weak Hadith can be used, neither of these lists are intended to be exhaustive. The general rule is weak Hadith are used for everything except for the fundamentals of creed or law. 

وَذَلِكَ كَالْمَوَاعِظِ، وَالْقِصَصِ، وَفَضَائِلِ الْأَعْمَالِ، وَسَائِرِ فُنُونِ التَّرْغِيبِ وَالتَّرْهِيبِ، وَسَائِرِ مَا لَا تَعَلُّقَ لَهُ بِالْأَحْكَامِ وَالْعَقَائِدِ (معرفة أنواع علوم الحديث)

And it includes reminders, stories, virtues of good deeds, every type of encouragement of good deeds and discouragement of sin, and everything that does not relate to legal ruling and creed. (Ibn al-Salah, al-Muqadimah).  

And Allah (Most High) knows best.

– Answered by Shaykh Noorud-deen (09.01.2021)

See also:

Using weak Hadith