It is Allah Who knows what they would have done
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ يُونُسَ، عَنِ ابْنِ شِهَابٍ، قَالَ وَأَخْبَرَنِي عَطَاءُ بْنُ يَزِيدَ، أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ، يَقُولُ سُئِلَ رَسُولُ اللَّهِ صلى الله عليه وسلم عَنْ ذَرَارِيِّ الْمُشْرِكِينَ فَقَالَ {اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ }
Narrated Abu Huraira: Allah's Messenger (ﷺ) was asked about the offspring of the pagans. He said, "Allah knows what they would have done (were they to live)."