Important Notes
1. The first part of the An-Nisa 4:137 ⧉ which begins with the words: إِنَّ الَّذِينَ آمَنُوا ثُمَّ كَفَرُوا (Surely, those who believed and then disbelieved, believed again and then disbelieved, then went on increasing in their disbelief) refers to the hypocrites. But, some commentators say that this verse An-Nisa 4:137 ⧉ is about the Jews for they were the ones who first believed, then, after having taken to the golden calf, became disbelievers. After that, they repented and believed. Then again, they rejected the prophethood of Sayyidna 'Isa علیہ و الصلوٰۃ السلام and fell back into disbelief. Finally, by refusing to believe in the prophethood of Sayyidna Muhammad ﷺ ، they further increased in their disbelief (Ruh al-Ma’ ani).
2. The second part of the An-Nisa 4:137 ⧉ لَّمْ يَكُنِ اللَّـهُ لِيَغْفِرَ لَهُمْ وَلَا لِيَهْدِيَهُمْ سَبِيلًا Allah is not to forgive them nor lead them on the path), when read as a whole with the first part, would mean that their repeated return to disbelief will cause their very ability to receive true guidance to be taken away from them and, in that event, they will have neither the future option to repent nor the opportunity to believe. Otherwise, the general rule laid out by the definitive texts of the Qur'an and ' Sunnah is that a disbeliever (kafir) or an apostate (مُاتَد murtadd), no matter how hardened, has his past sins forgiven -- if the taubah (repentance) made by him is sincere and true. So, if such, people too change and repent, the law of amnesty and forgiveness is open.