The Four Sources in Brief

Four pillars hold up the law: All the rulings of Islam rest on four sources, called the Adilla Arba'a (the Four Evidences). They are: Al-Kitab (the Quran), Al-Sunna (the teaching of the Prophet (SAW) and the Imams (as)), Al-'Aql (reason), and Al-Ijma' (the consensus of scholars).

The Shia difference is real: In Shia Usul, the Sunna includes the words, actions, and approvals of the Twelve Imams (as) as well as the Prophet (SAW), because the Imams (as) are infallible (Ma'sum) and the inheritors of the Prophet's (SAW) knowledge. Reason is an independent source, not just a tool. And Qiyas (reasoning by analogy) is rejected — the Imams (as) clearly prohibited it.

The sources work as one system: The Quran comes first, the Sunna explains it, reason confirms it and draws out what follows from it, and Ijma' points back to the teaching of the Imam (as). They are not four separate choices the jurist picks from freely — they must be used together, in their proper order.

Example

A house stands on four pillars. Remove one pillar and the roof sags; remove two and the house falls. In the same way, the rulings of Islam stand on four sources working together — the Quran, the Sunna, reason, and consensus.

Key Terms

• Adilla Arba'a (الادلہ الاربعہ) — the Four Evidences: Quran, Sunna, 'Aql, Ijma'
• Qiyas (قیاس) — reasoning by analogy; rejected in Shia Usul
• Ma'sum (معصوم) — infallible; protected by Allah from error and sin

Quran or Hadith

Imam al-Sadiq (as) said: "The Shari'a cannot be derived by analogy — whoever derives rulings by analogy has destroyed both himself and those who follow him." — to be checked. This is why Shia Usul rejects Qiyas and uses 'Aql instead.

Fresh diagram to be drawn: Four pillars holding up a roof labelled "Islamic Law" — the pillars labelled Quran, Sunna, 'Aql, Ijma', with the Quran pillar tallest.