Ibn Kathir (Abridged)
Hafiz Ibn Kathirوَلِكُلِّ أُمَّةٍ(And every Ummah has), meaning, each generation and nation, أَجَلٌ فَإِذَا جَآءَ أَجَلُهُمْ(its appointed term; when their term comes) which they were destined for, لاَ يَسْتَأْخِرُونَ سَاعَةً وَلاَ يَسْتَقْدِمُونَ(neither can they delay it nor can they advance it an hour (or a moment)). Allah then warned the Children of Adam that He sent to them Messengers who conveyed to them His Ayat. Allah also conveyed good news, as well as warning, فَمَنِ اتَّقَى وَأَصْلَحَ(then whosoever has Taqwa and becomes righteous) by abandoning the prohibitions and performing acts of obedience, فَلاَ خَوْفٌ عَلَيْهِمْ وَلاَ هُمْ يَحْزَنُونَوَالَّذِينَ كَذَّبُواْ بِـَايَـتِنَا وَاسْتَكْبَرُواْ عَنْهَآ(on them shall be no fear nor shall they grieve. But those who reject Our Ayat and treat them with arrogance,) meaning, their hearts denied the Ayat and they were too arrogant to abide by them, أُولَـئِكَ أَصْحَـبُ النَّارِ هُمْ فِيهَا خَـلِدُونَ(they are the dwellers of the Fire, they will abide therein forever.) without end to their dwelling in it.