مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3010
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas (رضي الله عنه) that The Prophet (ﷺ) was asked about the children of the mushrikeen [who died in childhood]. He said: "Allah knew best what they would have done when He created them."
Musnad Ahmad 3034Its isnad is saheeh, Muslim (2660)].