$50/month have 6x lifetime value. Users who refer three friends have 2x retention. But what’s the *compound interest* on impact? Measure net promoter score (NPS) for “trust that this product serves my long-term good.” That’s your leading indicator.

Qualitative: Run a diary study. Ask 20 users to log every time they feel their money is “doing good” beyond themselves. Code the responses. Themes emerge: *“I want my savings to mean something after I’m gone,” “I’d pay a small fee if it went to a cause I believe in,” “I don’t trust the bank to do good—I want control.”*

**MUJTAHID:**  
*Daleel* hierarchy: We need evidence that this feature is *maslaha* (public benefit) and not *munkar* (harm).  

1. **Qati al-Thubut, Zanni al-Dalala:** The hadith on sadaqah jariyah is authentic (qati al-thubut) but its application to product features is interpretive (zanni al-dalala). So we need *qiyas* (analogy).  
2. **Qiyas:** Compare a digital product that automates charitable giving to a physical endowment (waqf). The `'illah` (effective cause) is *continuity of benefit*. If a waqf building generates rent for a school, a product feature that auto-distributes micro-donations from savings generates ongoing benefit.  
3. **Istihsan (juristic preference):** Allow innovation in delivery mechanism as long as the maqsad (preservation of mal and din) is served.  
4. **Maslaha Mursalah (unrestricted benefit):** This feature does not contradict any text; it aligns with the maqsad of preserving wealth (mal) by making it fructify in the akhirah.

**Evidence Prompt Applied:**  
What is the “interest rate” on product impact? Calculate **Impact ROI**:  
```
Impact ROI = (Total benefit accrued to users over 10 years) / (Cost to build + maintain)
```
Example: A $50k feature that enables 10,000 users to each give $100/year to charity for 10 years = $10M in sadaqah. Impact ROI = 200x. That’s compound.

Measure generational impact: Track *second-degree referrals*—users whose parents used your feature. If a user sets up a legacy account, and their child later uses the same feature, that’s generational compound.

**Synthesis:**  
Evidence supports building a “Legacy Savings” module. Quantitative data shows users with long-term trust stay longer. Qualitative data shows desire for afterlife impact. Islamic daleel validates the mechanism as sadaqah jariyah via qiyas on waqf. The `'illah` is continuity. The maqsad is preservation of din and mal.

---

### 4. SHURA (CONSULTATION)

**PRODUCT_LEAD:**  
Call a cross-functional sync. Invite Engineering, Legal, Compliance, and Customer Support.  

- **Engineering:** “Can we build a rule engine that lets users set recurring charitable allocations from savings? Yes, but we need API integration with Islamic charities.”  
- **Legal/Compliance:** “Are there regulatory implications for ‘estate planning’ features? We need to avoid giving financial advice. Frame it as a ‘giving tool’ not a will.”  
- **Customer Support:** “Users will call confused. We need clear onboarding and a fatwa verification badge.”  

Interview three religious scholars (or Shari’ah advisors) separately. Ask: *“Is this a valid form of sadaqah jariyah? What conditions must we meet?”* One scholar says: “The user must intend sadaqah at the time of setting up. The charity must be reputable. The mechanism must not involve riba or gharar.”

**MUJTAHID:**  
*Shura* in Usul al-Fiqh is not a vote; it’s a consultation that uncovers blind spots. The Mujtahid must weigh input by *adalah* (integrity) and *khibra* (expertise).  

- Weight the scholar’s input highest (expertise in Shari’ah).  
- Weight engineering input second (feasibility).  
- Weight legal input third (regulatory risk).  

Record dissent. One compliance officer says: *“This blurs the line between product and philanthropy. We might be seen as a non-profit.”* The Mujtahid notes this as a *shubha* (doubt) to address via *sad al-dhara’i* (blocking the means to harm). Solution: Clear disclaimers that the feature is a tool, not a charitable institution.

**Shura Prompt Applied:**  
How do you consult? Schedule a 90-minute session. Open with the maqsad: *“We want to build a product that becomes sadaqah jariyah. What do we need to make it valid, trustworthy, and scalable?”*  

- Read aloud the hadith on sadaqah jariyah.  
- Show the qiyas to waqf.  
- Ask each stakeholder: *“What could go wrong? What are we missing?”*  

Close by summarizing three **shurut** (conditions) that emerged from shura:  
1. User must make intention (niyyah) at setup.  
2. Charity recipient must be verified.  
3. No riba in the underlying savings product.

**End of Part 1.**