Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:2:179 –

And there is for you in legal retribution ˹saving of˺ life, O you ˹people˺ of understanding, that you may become righteous.  

In retaliation there is life for you, that is great longevity, O people of pith, possessors of intellect, because if the would-be killer knew that he would be killed ˹in retaliation˺, he would refrain ˹from such action˺ and would have thereby given life to himself and to the one whom he had intended to kill; and so it ˹retaliation˺ was stipulated by the Law, so that you might fear killing, fearing retaliation.
القرآن:٢:١٧٩ –

وَلَكُمْ فِي الْقِصَاصِ حَيَاةٌ يَا أُولِي الْأَلْبَابِ لَعَلَّكُمْ تَتَّقُونَ  

{ولكم في القصاص حياة} أي بقاء عظيم {يا أولي الألباب} ذوي العقول لأن القاتل إذا علم أنه يُقتل ارتدع فأحيا نفسه ومن أراد قتله فشرع {لعلكم تتقون} القتل مخافة القود.