The nature of kufr (disbelief)

وَإِذَا قَرَأْتَ ٱلْقُرْءَانَ جَعَلْنَا بَيْنَكَ وَبَيْنَ ٱلَّذِينَ لَا يُؤْمِنُونَ بِٱلْـَٔاخِرَةِ حِجَابًا مَّسْتُورًا

And when you recite the Qur’ān, We put between you and those who do not believe in the Hereafter a concealed partition.