How do we harmonize between:
(لِتُنْذِرَ قَوْمًا مَا أُنْذِرَ آبَاؤُهُمْ فَهُمْ غَافِلُونَ)
“In order that you may warn a people whose forefathers were not warned, so they are heedless.”
[Surat Ya-Seen 6]
(إِنَّا أَرْسَلْنَاكَ بِالْحَقِّ بَشِيرًا وَنَذِيرًا ۚ وَإِنْ مِنْ أُمَّةٍ إِلَّا خَلَا فِيهَا نَذِيرٌ)
“Verily! We have sent you with the truth, a bearer of glad tidings, and a warner. And there never was a nation but a warner had passed among them.”
[Surat Fatir 24]
Pertaining to the verse:
﴿لِتُنذِرَ قَوْماً مَّآ أُنذِرَ ءَابَآؤُهُمْ فَهُمْ غَـفِلُونَ ﴾
(In order that you may warn a people whose forefathers were not warned, so they are heedless.)
The scholars have differed amongst themselves on the meaning of this verse. Some said it means that since the other verse is only affirming that generally every nation has a warner (and not negating the possibility of the warners’ warnings not reaching some individuals from a nation), then (some scholars believe that these scarce individuals) will thus be tested on the Day of Resurrection.
And some said the verse actually means:
لِتُنذِرَ قَوْماً كمَّآ أُنذِرَ ءَابَآؤُهُمْ فَهُمْ غَـفِلُونَ
With addition of a ك (the letter kaaf), so it means then:
(In order that you may warn a people whose forefathers were likewise warned, so they are heedless (due to them turning away from the warning) .
There are a few opinions al-Imam Shinqeeti mentioned regarding it, perhaps it can be mentioned in detail later inshaa Allah.
AbdulFattaah bin Uthman