Inheritance Calculation According to Muhammad ibn Ali ar-Rahabi

The science of fara’idh through Matn ar-Rahbiyyah (“Bughyat al-Bahits ‘an Jumal al-Mawarits”) — a 176-verse nazham by ar-Rahabi (497–577 AH) that became the most widely memorized fara’idh textbook for nine centuries, following the Shafi’i madhhab / Zayd ibn Thabit’s system path. Sixteen files: theory following the matn’s flow, the calculation engine, the three major Shafi’i distinguishing marks, six case studies, and a comparison of Warismatika’s three paths.

Summary (TL;DR)

Ar-Rahbiyyah teaches fara’idh according to the madhhab of Zayd ibn Thabit — the Companion the Prophet ﷺ named as most knowledgeable in fara’idh — as adopted by the Shafi’is. The core rules are the same across all paths (fixed shares, ‘ashabah, hajb, ‘awl, tashih), but four distinctive positions change the numbers: the grandfather shares with siblings via muqasamah; a remainder with no ‘ashabah goes to bayt al-mal (no radd); dzawil arham do not inherit; and full siblings join tashrik in the maternal siblings’ 1/3 in Mushtarakah. Later Shafi’i scholars shifted two of these middle positions toward radd/dzawil arham inheritance when bayt al-mal is not well-organized — directly relevant for Indonesia.

Key points:

• This is the path of Indonesian pesantren tradition: the matn’s version of the calculation is what a Shafi’i-madhhab setting will expect.
• The four distinguishing marks above are the entire practical difference from the previous two bundles; everything else is identical (chapter 13 maps it in one table).
• The bayt al-mal vs. radd case is calculated side by side in rupiah (chapter 12) — the difference is real, not theoretical.
• Key verses are quoted so you can feel how the nazham works as a memorization tool (chapter 01).
• A learning tool, not a fatwa — for real distributions: one system, its points of disagreement named, and the Religious Courts for official validation.

5W+1H

Question	Short answer	Chapter
What	Fara’idh per the classical Shafi’i verse-matn (Zayd’s system)	01–02
Why	A 9-century standard matn; the system used by Indonesia’s Shafi’i tradition	01, 13
Who	Ar-Rahabi (497–577 AH, Rahbah, Shafi’i); Zayd ibn Thabit’s system; 10+7 heirs	01–04
When	After death is certain + rights that precede inheritance	02
Where	Shafi’i fiqh across countries + notes on Indonesia’s bayt al-mal/KHI	07, 13
How	The 7-step procedure + tashih/munasakhat + Zayd’s system for the grandfather	05–09, practice 10–12

Concept map: how the calculation works

flowchart TB
  classDef start fill:#374151,stroke:#9ca3af,color:#f3f4f6
  classDef core fill:#134e4a,stroke:#14b8a6,color:#ccfbf1
  classDef how fill:#713f12,stroke:#ca8a04,color:#fef9c3
  classDef out fill:#1e3a8a,stroke:#3b82f6,color:#dbeafe
  H["The estate left behind"]:::start --> R["Subtract: burial costs, debts, bequests (max 1/3)"]:::start
  R --> T["TIRKAH — the estate to divide"]:::core
  T --> F["Ashabul furudh — fixed shares<br/>1/2 · 1/4 · 1/8 · 2/3 · 1/3 · 1/6"]:::core
  T --> A["'Ashabah — take the residue<br/>(nearest male relatives)"]:::core
  F --> HJ["Filter by HAJB<br/>the nearer blocks the farther"]:::how
  A --> HJ
  HJ --> K["Correct if it doesn't fit<br/>'awl · radd · tashih"]:::how
  K --> D["Final share for each heir"]:::out

This flow is shared across the classical paths; ar-Rahabi’s hallmark (Zayd / Shafi’i system): grandfather muqasamah, no radd (residue to bayt al-mal), and tashrik in Musytarakah.

Reading order

1. 01 — Big picture and ar-Rahabi
2. 02 — Foundations: causes & impediments
3. 03 — Fixed-share heirs by number · 04 — Ta’sib & hajb
4. 05 — Calculation engine · 06 — Tashih & munasakhat
5. 07 — ‘Awl & bayt al-mal · 08 — Zayd’s system · 09 — Tashrik & special cases ← the three distinguishing marks
6. 10 · 11 · 12 — case studies
7. 13 — Comparison of three paths · 14 — Glossary · 15 — References

Prerequisites & notes

• Prerequisite: fraction arithmetic. Stands alone, but reads best as the third path after the Ibn Uthaymin bundle and al-Fawzan.
• Fiqh position: Zayd’s system is presented as the matn’s position; the muta’akhkhirin exception and contemporary tarjih are flagged where they occur.
• The Indonesian version is in the sibling bundle: perhitungan-waris-ar-rahabi-id/.