Qiṣāṣ concerns a grave response to the taking of life, while ḥayāh denotes life. Their deliberate pairing invites a question: how can a legal sanction for homicide be associated with life?
The answer lies in deterrence and limitation of further unlawful violence under a justly enforced legal framework. The verse joins an outward contrast with a substantive causal relationship, conveying in one phrase what would otherwise require much explanation.