Al-Nawawī gives distinct reasons why hadith specialists recorded some reports from transmitters whom they criticized.
**First**, a weak route can be written down for **iʿtibār and istishhād**, to compare or corroborate chains, without being an independent proof. **Second**, one generally weak narrator may preserve particular material that deserves separate examination through other routes. The reported statement of Sufyān al-Thawrī that he could distinguish that transmitter’s true reports from his false ones does not authenticate every report in advance.
**Third**, the commentary allows limited leniency with certain non-fabricated reports about **exhortation, warning and virtues**, where the underlying conduct already has an established basis in religion. This is not license to use a weak report independently to institute a legal obligation, permit or prohibit an act. Fabricated (**mawḍūʿ**) material is excluded. **Fourth**, a scholar can preserve a weak route while disclosing its defect, without presenting it unqualified as a binding rule.
**Compare:** “This additional chain is recorded with its weakness stated” is scholarly comparison; “This weak chain independently proves an obligation” falsely inflates its evidentiary weight.