Allah criticizes the Jews and Christians who claim to follow their Books, the Tawrah and the Injil, because when they are called to refer to these Books where Allah commanded them to follow Muhammad , they turn away with aversion. This censure and criticism from Allah was all because of their defiance and rejection. Allah said next,

ذَلِكَ بِأَنَّهُمْ قَالُواْ لَن تَمَسَّنَا النَّارُ إِلاَ أَيَّامًا مَّعْدُودَتٍ

(This is because they say: "The Fire shall not touch us but for a number of days.") meaning, what made them dare to challenge and defy the truth is their false claim that Allah will only punish them for seven days in the Fire, a day for every one thousand years in this life. We mentioned this subject in the Tafsir of Surat Al-Baqarah.

Allah then said,

وَغَرَّهُمْ فِى دِينِهِم مَّا كَانُواْ يَفْتَرُونَ

(And that which they used to invent regarding their religion has deceived them.) meaning, what caused them to remain on their false creed is that they deceived themselves, believing that the Fire will only touch them for a few days for their errors. However, it is they who have invented this notion, and Allah did not grant them authority to support this claim. Allah said, while threatening and warning them,

فَكَيْفَ إِذَا جَمَعْنَـهُمْ لِيَوْمٍ لاَّ رَيْبَ فِيهِ

(How (will it be) when We gather them together on the Day about which there is no doubt (i. e. the Day of Resurrection).) meaning, what will their condition be like after they have uttered this lie about Allah, rejected His Messengers and killed His Prophets and their scholars who enjoined righteousness and forbade evil Allah will ask them about all this and punish them for what they have done. This is why Allah said,

فَكَيْفَ إِذَا جَمَعْنَـهُمْ لِيَوْمٍ لاَّ رَيْبَ فِيهِ

(How (will it be) when We gather them together on the Day about which there is no doubt.) meaning, there is no doubt that this Day will come,

وَوُفِّيَتْ كُلُّ نَفْسٍ مَّا كَسَبَتْ وَهُمْ لاَ يُظْلَمُونَ

(And each person will be paid in full what he has earned And they will not be dealt with unjustly.).