حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عِمْرَانَ، حَدَّثَنَا أَبُو دَاوُدَ، حَدَّثَنَا هِشَامُ بْنُ أَبِي الْوَلِيدِ، عَنْ أُمِّهِ، عَنْ فَاطِمَةَ بِنْتِ الْحُسَيْنِ، عَنْ أَبِيهَا الْحُسَيْنِ بْنِ عَلِيٍّ، قَالَ لَمَّا تُوُفِّيَ الْقَاسِمُ ابْنُ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَتْ خَدِيجَةُ يَا رَسُولَ اللَّهِ دَرَّتْ لُبَيْنَةُ الْقَاسِمِ فَلَوْ كَانَ اللَّهُ أَبْقَاهُ حَتَّى يَسْتَكْمِلَ رَضَاعَهُ ‏.‏ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِنَّ تَمَامَ رَضَاعِهِ فِي الْجَنَّةِ ‏"‏ ‏.‏ قَالَتْ لَوْ أَعْلَمُ ذَلِكَ يَا رَسُولَ اللَّهِ لَهَوَّنَ عَلَىَّ أَمْرَهُ ‏.‏ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِنْ شِئْتِ دَعَوْتُ اللَّهَ تَعَالَى فَأَسْمَعَكِ صَوْتَهُ ‏"‏ ‏.‏ قَالَتْ يَا رَسُولَ اللَّهِ بَلْ أُصَدِّقُ اللَّهَ وَرَسُولَهُ ‏.‏

Husainbin ‘Ali said: “When Qasim the son of the Messenger of Allah(PBUH) died, Khadijah said: ‘O Messenger of Allah, the milk ofQasim’smother is overflowing. Would that Allah had let him liveuntil he hadfinished breastfeeding.’ The Messenger of Allah (PBUH)said: ‘He willcomplete his breastfeeding in Paradise.’ She said:‘If I know that, OMessenger of Allah, it makes it easier for me tobear.’ The Messengerof Allah (PBUH) said: ‘If you wish, I willpray to Allah to let youhear his voice.’ She said: ‘O Messengerof Allah, rather I believeAllah and His Messenger.’” Translation Not Available

Book Ref: Sunan Ibn Majah Book 6 Hadith 1512
Web Ref:  Sunan Ibn Majah Vol 1 Book 6 Hadith 1512