The Prophet ﷺ said, "No Muslim whose three children died will go to the Fire except for Allah's oath (i.e. everyone has to pass over the bridge above the lake of fire)."  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ يَمُوتُ لِمُسْلِمٍ ثَلاَثَةٌ مِنَ الْوَلَدِ فَيَلِجَ النَّارَ إِلاَّ تَحِلَّةَ الْقَسَمِ قَالَ أَبُو عَبْدِ اللَّهِ {وَإِنْ مِنْكُمْ إِلاَّ وَارِدُهَا}  

A woman came to Messenger of Allah ﷺ and said, "O Messenger of Allah ﷺ! Men (only) benefit by your teachings, so please devote to us from (some of) your time, a day on which we may come to you so that you may teach us of what Allah has taught you." Messenger of Allah ﷺ said, "Gather on such-and-such a day at suchand- such a place." They gathered and Messenger of Allah ﷺ came to them and taught them of what Allah had taught him. He then said, "No woman among you who has lost her three children (died) but that they will screen her from the Fire." A woman among them said, "O Messenger of Allah ﷺ! If she lost two children?" She repeated her question twice, whereupon the Prophet ﷺ said, "Even two, even two, even two!" (See Hadith No. 341, Vol. 2)  

عَنْ أَبِي سَعِيدٍ جَاءَتِ امْرَأَةٌ إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَتْ يَا رَسُولَ اللَّهِ ذَهَبَ الرِّجَالُ بِحَدِيثِكَ فَاجْعَلْ لَنَا مِنْ نَفْسِكَ يَوْمًا نَأْتِيكَ فِيهِ تُعَلِّمُنَا مِمَّا عَلَّمَكَ اللَّهُ فَقَالَ اجْتَمِعْنَ فِي يَوْمِ كَذَا وَكَذَا فِي مَكَانِ كَذَا وَكَذَا فَاجْتَمَعْنَ فَأَتَاهُنَّ رَسُولُ اللَّهِ ﷺ فَعَلَّمَهُنَّ مِمَّا عَلَّمَهُ اللَّهُ ثُمَّ قَالَ مَا مِنْكُنَّ امْرَأَةٌ تُقَدِّمُ بَيْنَ يَدَيْهَا مِنْ وَلَدِهَا ثَلاَثَةً إِلاَّ كَانَ لَهَا حِجَابًا مِنَ النَّارِ فَقَالَتِ امْرَأَةٌ مِنْهُنَّ يَا رَسُولَ اللَّهِ اثْنَيْنِ قَالَ فَأَعَادَتْهَا مَرَّتَيْنِ ثُمَّ قَالَ وَاثْنَيْنِ وَاثْنَيْنِ وَاثْنَيْنِ  

as above (the sub narrators are different). Abu Huraira qualified the three children referred to in the above mentioned Hadith as not having reached the age of committing sins (i.e. age of puberty) .  

عَنِ النَّبِيِّ ﷺ بِهَذَا وَعَنْ عَبْدِ الرَّحْمَنِ بْنِ الأَصْبَهَانِيِّ قَالَ سَمِعْتُ أَبَا حَازِمٍ عَنْ أَبِي هُرَيْرَةَ قَالَ ثَلاَثَةً لَمْ يَبْلُغُوا الْحِنْثَ