Separation of believers from disbelievers

لِيَمِيزَ ٱللَّهُ ٱلْخَبِيثَ مِنَ ٱلطَّيِّبِ وَيَجْعَلَ ٱلْخَبِيثَ بَعْضَهُۥ عَلَىٰ بَعْضٍ فَيَرْكُمَهُۥ جَمِيعًا فَيَجْعَلَهُۥ فِى جَهَنَّمَ ۚ أُو۟لَـٰٓئِكَ هُمُ ٱلْخَـٰسِرُونَ

[It is] so that Allāh may distinguish the wicked from the good and place the wicked some of them upon others and heap them all together and put them into Hell. It is those who are the losers.

قَالَ يَـٰنُوحُ إِنَّهُۥ لَيْسَ مِنْ أَهْلِكَ ۖ إِنَّهُۥ عَمَلٌ غَيْرُ صَـٰلِحٍ ۖ فَلَا تَسْـَٔلْنِ مَا لَيْسَ لَكَ بِهِۦ عِلْمٌ ۖ إِنِّىٓ أَعِظُكَ أَن تَكُونَ مِنَ ٱلْجَـٰهِلِينَ

He said, "O Noah, indeed he is not of your family; indeed, he is [one whose] work was other than righteous, so ask Me not for that about which you have no knowledge. Indeed, I advise you, lest you be among the ignorant."

قَالَ قَآئِلٌ مِّنْهُمْ إِنِّى كَانَ لِى قَرِينٌ

A speaker among them will say, "Indeed, I had a companion [on earth].