Mishkat al-Masabih #110

‘Ali said that Khadija asked the Prophet about two children of hers who had died in the pre-Islamic period and God’s messenger replied, “They are in hell.” Then when he saw her look of disapproval he said, “If you saw their position you would hate them.” She asked, “Messenger of God, what about my son whom I had from you?” He replied, “He is in paradise.” Then God’s messenger said, “The believers and their children are in paradise and the polytheists and their children are in hell.” Then God’s messenger recited, “Those who believe and whose offspring have followed them.” Ahmad transmitted it.