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:4:93 –

But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allah has become angry with him and has cursed him and has prepared for him a great punishment.  

And whoever slays a believer deliberately, intending to kill him, with something that is lethal, aware of the fact that he ˹the slain˺ is a believer, his requital is Hell, abiding therein, and God is wroth with him and has cursed him, He has removed him from His mercy, and has prepared for him a mighty chastisement, in the Fire: this may be explained as ˹referring to˺ the person that deems such ˹killing˺ licit, or as being his requital if he were to be requited, but it would not be anything new if this threat ˹of punishment˺ were to be forgone, because of what He says: Other than that ˹that is, idolatry˺ He forgives whomever He will ˹Q. 4:48˺. It is reported from Ibn ‘Abbās that it ˹the verse˺ should be understood as it stands, abrogating other verses of ‘forgiveness’. The verse in ˹sūrat˺ al-Baqara ˹Q. 2:178˺ clearly indicates that the one who kills deliberately should be killed in return, or if he is pardoned then he has to pay the blood-money, the value of which has already been mentioned. It is made clear in the Sunna that between the intentional and the unintentional, there is a type of killing that is identified as ˹being with˺ quasi-deliberate intent (shibh al‘amd), where the killer has slain with what in most cases is not ˹a˺ lethal ˹implement˺. In such a case, there is no ˹right to˺ retaliation and blood-money is paid instead, so that it ˹this type of killing˺ is described as intentional, but ˹considered˺ unintentional in ˹that there applies˺ the fixing of the period ˹for payment˺ and the sharing of the burden ˹by the killer’s clan˺; in this ˹case˺ and that of intentional killing redemption is more urgent than in unintentional killing.
القرآن:٤:٩٣ –

وَمَنْ يَقْتُلْ مُؤْمِنًا مُتَعَمِّدًا فَجَزَاؤُهُ جَهَنَّمُ خَالِدًا فِيهَا وَغَضِبَ اللَّهُ عَلَيْهِ وَلَعَنَهُ وَأَعَدَّ لَهُ عَذَابًا عَظِيمًا  

{ومن يقتل مؤمنا متعمِّدا} بأن يقصد قتله بما يقتل غالبا عالما بإيمانه {فجزاؤه جهنم خالدا فيها وغضب الله عليه ولعنه} أبعده من رحمته {وأعد له عذابا عظيما} في النار وهذا مؤوَّل بمن يستحله أو بأن هذا جزاؤه إن جُوزي ولا يدفع في خلف الوعيد لقوله (ويغفر ما دون ذلك لمن يشاء) وعن ابن عباس أنها على ظاهرها وأنها ناسخة لغيرها من آيات المغفرة وبينت آية البقرة أن قاتل العمد يقتل به وأن عليه الدية إن عفي عنه وسبق قدرها وبينت السنة أن بين العمد والخطأ قتلا يسمى شبه العمد وهو أن يقتله بما لا يقتل غالبا فلا قصاص فيه بل دية كالعمد في الصفة والخطأ في التأجيل والحمل وهو والعمد أولى بالكفارة من الخطأ.