Mishkat al-Masabih 84
‘A’isha said:
God’s messenger was invited to the funeral of a boy who belonged to the Ansar and I said, “Messenger of God, this one is blessed; he is one of the young ones 1 in paradise, for he has done no evil, being too young for that.” He replied, “It may be otherwise, ‘A’isha, for God has created some to go to paradise, doing so when they were still in their fathers’ loins; and He has created others for hell, doing so when they were still in their fathers’ loins.” 

Muslim transmitted it. 1 Lit. small birds or sparrows.
عَن عَائِشَة أم الْمُؤمنِينَ قَالَتْ: «دُعِيَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِلَى جِنَازَةِ صَبِيٍّ مِنَ الْأَنْصَارِ فَقُلْتُ يَا رَسُولَ اللَّهِ طُوبَى لِهَذَا عُصْفُورٌ مِنْ عَصَافِيرِ الْجَنَّةِ لَمْ يَعْمَلِ السُّوءُ وَلَمْ يُدْرِكْهُ قَالَ أَوَ غَيْرُ ذَلِكِ يَا عَائِشَةُ إِنَّ اللَّهَ خَلَقَ لِلْجَنَّةِ أَهْلًا خَلَقَهُمْ لَهَا وَهُمْ فِي أَصْلَابِ آبَائِهِمْ وَخَلَقَ لِلنَّارِ أَهْلًا خَلَقَهُمْ لَهَا وهم فِي أصلاب آبَائِهِم» . رَوَاهُ مُسلم