Zayd bin Thabit reported,
When the verse in al-Furqan was revealed, "And those who do not invoke another god alongside Allah, nor kill the soul which Allah has forbidden except in the course of justice" [Furqan 25:68], we marveled at its leniency. We waited six months, then the verse in Surah an-Nisa was revealed, "And whoever kills a believer intentionally, his recompense is Hell, abiding therein eternally" [Nisa 4:93]. That is, the severe verse was revealed after the lenient one and abrogated it. By "the severe" he meant this latter verse, and by "the lenient" he meant the verse of al-Furqan.
Azami 12196
Hasanعن زيد بن ثابت قال
لما نزلت هذه الآية التي في الفرقان: {والذين لا يدعون مع الله إلها واخر ولا يقتلون النفس التي حرم الله إلا بالحق}[سورة الفرقان: ٦٨] عجبنا للينها، فلبثنا ستة أشهر، ثم نزلت التي في سورة النساء: {ومن يقتل مؤمنا متعمدا فجزاؤه جهنم خلدا فيها} أي ثم نزلت الغليظة بعد اللينة. فنسخت اللينة. وأراد بالغليظة هذه الآية وباللينة آية الفرقان.
Nasai narrated it (7/87), Abu Dawud (4272), Tabarani in al-Kabir (5/136-137), and Ibn Jareer Tabari in his Tafsir (7/349), all of them through the hadith of Abu Zinad, from Kharija bin Zayd, from his father, mentioning it as above. Some of them inserted "Mujalid bin Awf" between Abu Zinad and Kharija, and both chains are preserved. The narrators from Abu Zinad are not all trustworthy, but they strengthen one another, and through them the hadith becomes hasan.In this verse there is a severe threat and a firm warning for one who kills a believer intentionally. Allah Almighty has paired it with shirk against Allah in more than one verse of His noble Book. For this reason Ibn Abbas held the view that there is no repentance for one who kills intentionally. Ibn Abu Hatim, in his Tafsir (3/1037), transmitted something similar from Zayd bin Thabit, Abu Hurairah, Ibn Umar, Abu Salama, Ubayd bin Umayr, Hasan, Dahhak, and Qatada, who said, "He has no repentance." And the verse is definitive.The majority of scholars, both from the early and later generations, held that the killer does have repentance between himself and his Lord 
. If he repents, turns back, humbles himself, submits, and does righteous deeds, Allah will exchange his bad deeds for good ones, compensate the slain person for the wrong done to him, and satisfy his claim (Ibn Kathir).Allah Almighty has said, "Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And whoever associates others with Allah has committed a tremendous sin" [Nisa 4:48]. This is general, covering all sins except shirk.As for the noble verse, "And whoever kills a believer intentionally, his recompense is Hell, abiding therein forever. Allah's wrath is upon him, and He has cursed him and prepared for him a great punishment" [Nisa 4:93], Abu Hurairah said, "That is his recompense, if He chooses to recompense him." Ibn Abu Hatim mentioned this in his Tafsir, and it was also related from others.As for His words "abiding therein forever" [Nisa 4:93], this means a long stay, since it has been established in the mutawatir hadiths that permanent, eternal abiding belongs only to one who commits shirk or disbelief.