Abu Mijlaz (may Allah have mercy on him) said concerning this saying of Allah Almighty, 'And whoever kills a believer intentionally' [Surah al-Nisa: 93]: That is indeed his recompense, but if Allah Almighty wills, He can also forgive him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15829