One may expand the sense in explanation by mentioning deterrence from killing or fear of lawful retaliation. Such reconstruction can clarify the causal connection, but it does not prove that an indispensable phrase is grammatically or rhetorically absent from the verse.
If fī l-qiṣāṣi ḥayāh already conveys the intended relation in its actual wording, it remains an example of ījāz al-qaṣr. Explanatory paraphrase and technical ellipsis are not the same judgment.