مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1844
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn "Abbas that the Prophet (ﷺ) was asked about the children of the mushrikeen (who died). He said: "Allah knows best what they would have done."
Musnad Ahmad 1845Sahih hadeeth]