“Ḍiʿfa al-ḥayāti wa-ḍiʿfa al-mamāt”
“Double [punishment] in life and double [punishment] in death.” (al-Isrāʾ 17:75, excerpt)
The phrase is not about doubling the length of life or death. The surrounding warning concerns a double punishment in those states, expressible by supplying the implied noun “punishment.”
This illustrates how context can identify the substantive noun behind an abbreviated genitive expression. A valid reconstruction must reflect the subject matter of the verse rather than merely supply any grammatically conceivable word.
As a parallel, “double the hardship of travel” concerns the hardship encountered while travelling, not twice the journey’s calendar dates.
“Man fī al-samāwāti wa-al-arḍ”
“Those who are in the heavens and the earth.” (al-Raḥmān 55:29, excerpt)
The collective reference is interpreted through context; it should not be narrowed to one group without evidence.