وَحُكْمُ الْخَفِيِّ: وُجُوبُ الطَّلَبِ حَتَّى يَزُولَ عَنْهُ الْخَفَاءُ.
The rule for khafī is to investigate until the source of obscurity is resolved.
The ordinary legal sense of zinā is clear, yet whether another prohibited sexual act falls under the very same prescribed classification is debated among jurists. The difficulty lies in applying a known category to a legally different act.
Similarly, an oath not to eat “fruit” may raise questions about customary classification of particular foods. Context, usage, and legally relevant conditions must be investigated; partial resemblance is not sufficient proof of identical treatment.