Is there actually any difference between Usul-Din and Usul-Fiqh?
Which one should I go for if want to become a mufti?
Usul-al-Din means (Principles of the Religion) while Usul-al-Fiqh means (Principles of Jurisprudence).
The Principles of Religion (Usul al-Din) which outline the essential beliefs in accordance with the Qur’an and the teachings of the Twelve Imams
The Principles of the Religion according to Twelver Shi’a Islam are:
- Belief in Oneness and Unity of God: Al-Tawhid
- Belief in Divine Justice: Al-Adl
- Belief in Prophethood: Al-Nubuwah
- Belief in Imams: Al-Imamah
- Belief in Day of Resurrection: Al-Ma’ad
In Sunni Islam, the equal would be iman mufassal.
Principles of Islamic jurisprudence otherwise known as Uṣūl al-fiqh (Arabic: أصول الفقه) is the study and critical analysis of the origins, sources, and principles upon which Islamic jurisprudence is based.
The four main sources for Usul-al-Fiqh are:
They are analysed along with secondary sources:
- Masali Mursala
- Ihsaan (spiritual excellence, virtue)
- Urf (local custom or pre-existing law)
- Aql (reason or intellect)
- Sadd al-dharai
- Shara man qablana
- Ijma al-ummah (consensus of the worldwide Muslim community)
- Ijma khulafah al-rashideen (consensus of the first four caliphs)
- Ijma ahl al-medina (consensus of the Muslims of Medina, as reflected in early hadith collections, e. g. the Muwatta of Imam Malik ibn Anas)
- Ijma al-ullama (consensus of scholars of Islamic law)
- Ijma ahl al-hali wa al-aqd
These are used to discuss:
- General evidences and principles (adillah ijmalliya wa al-qawaid)
- Resolution of conflict and discrepancy (ta'adal wa tarjeeh)
- Determination of rules and adoption/emulation of rules (ijtihad wa taqlid)
- Islamic Law (hukm shari)
The Jafari Akhbari Shias believe that the Quran and Sunnah are the only sources of law while the Jafari Usuli Shias use Ijtihaad.
Conclusion: The difference between these two is that Usul-al-Din is principle of religion and beliefs while Usul-al-Fiqh is the principles of Islamic law, i.e. Sharia.
If one wants to become a Mufti, it depends whether you follow Sunni or Shia. According to Wikipedia:
A mufti (/ˈmʌfti/; Arabic: مفتي muftī; Turkish: müftü) is an Islamic scholar who interprets and expounds Islamic law (Sharia and fiqh).
Therefore one will need to learn Usul-al-Fiqh.
And Allah knows best.