Musnad Ahmad 30:1982

Husayn narrated to us, he said: Ibn Abi Dhi'b narrated to us, from al-Zuhri, from 'Ata' ibn Yazid al-Laythi, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him: That he was asked about the children of the polytheists? He said: "Allah is most knowing of what they would have been doing."