The Prophet ﷺ was asked about the children of the polytheists, and he said, "Allah knows best what they would have done."
حدثنا هشيم عن أبي بشر عن سعيد بن جبير
أن النبي ﷺ سئل عن ذراري المشركين فقال الله أعلم بما كانوا عاملين
Its isnad is sahih. Bukhari related it 3:195-196 through Shubah, and Muslim 2:302 through Abu Awana, both of them from Abu Bishr. It will come again at 3035.