Allah knows best about what they were doing.  

أَنَّ النَّبِيَّ ﷺ سُئِلَ عَنْ أَوْلاَدِ الْمُشْرِكِينَ فَقَالَ اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ  

I said : Messenger of Allah (May peace be upon him) what happens to the offspring of believers ? He replied : They are joined to their parents. I asked : Messenger of Allah! Although they have done nothing ? He replied : Allah knows best what they were doing. I asked : what happens to the offspring of polytheists, Messenger of Allah ? he replied! They are joined to their parents. I asked : Although they have done nothing? He replied : Allah knows best what they were doing.  

قُلْتُ يَا رَسُولَ اللَّهِ ذَرَارِيُّ الْمُؤْمِنِينَ فَقَالَ هُمْ مِنْ آبَائِهِمْ فَقُلْتُ يَا رَسُولَ اللَّهِ بِلاَ عَمَلٍ قَالَ اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ قُلْتُ يَا رَسُولَ اللَّهِ فَذَرَارِيُّ الْمُشْرِكِينَ قَالَ مِنْ آبَائِهِمْ قُلْتُ بِلاَ عَمَلٍ قَالَ اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ  

The Prophet (May peace be upon him) was invited to the funeral of a boy who belonged to the ANSAR and I said; Messenger of Allah! This one is blessed, for he has done no evil, nor has he known it. He replied : It may be otherwise, ‘A’ishah, for Allah created Paradise and created those who will go to it, and He created it for them when they were still in their father’s loins; and he created hell and created those who will go to it, and created it for them when they were still in their father’s loins.  

أُتِيَ النَّبِيُّ ﷺ بِصَبِيٍّ مِنَ الأَنْصَارِ يُصَلِّي عَلَيْهِ قَالَتْ قُلْتُ يَا رَسُولَ اللَّهِ طُوبَى لِهَذَا لَمْ يَعْمَلْ شَرًّا وَلَمْ يَدْرِ بِهِ فَقَالَ أَوَغَيْرَ ذَلِكَ يَا عَائِشَةُ إِنَّ اللَّهَ خَلَقَ الْجَنَّةَ وَخَلَقَ لَهَا أَهْلاً وَخَلَقَهَا لَهُمْ وَهُمْ فِي أَصْلاَبِ آبَائِهِمْ وَخَلَقَ النَّارَ وَخَلَقَ لَهَا أَهْلاً وَخَلَقَهَا لَهُمْ وَهُمْ فِي أَصْلاَبِ آبَائِهِمْ  

Every child is born on Islam, but his parents make him a Jew and a Christian, just as a beast is born whole. Do you find some among them (born) maimed? The people asked : Messenger of Allah! What do you think about the one who died while he was young? He replied : Allah knows best what he was going to do.  

قَالَ رَسُولُ اللَّهِ ﷺ كُلُّ مَوْلُودٍ يُولَدُ عَلَى الْفِطْرَةِ فَأَبَوَاهُ يُهَوِّدَانِهِ وَيُنَصِّرَانِهِ كَمَا تَنَاتَجُ الإِبِلُ مِنْ بَهِيمَةٍ جَمْعَاءَ هَلْ تُحِسُّ مِنْ جَدْعَاءَ قَالُوا يَا رَسُولَ اللَّهِ أَفَرَأَيْتَ مَنْ يَمُوتُ وَهُوَ صَغِيرٌ قَالَ اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ  

Malik was asked : The heretics argue from this tradition against us. Malik said : Argue against them from its last part which goes. The people asked : What do you think about the one who died while he was young? He replied : Allah knows best what he was going to do.  

سَمِعْتُ مَالِكًا قِيلَ لَهُ إِنَّ أَهْلَ الأَهْوَاءِ يَحْتَجُّونَ عَلَيْنَا بِهَذَا الْحَدِيثِ قَالَ مَالِكٌ احْتَجَّ عَلَيْهِمْ بِآخِرِهِ قَالُوا أَرَأَيْتَ مَنْ يَمُوتُ وَهُوَ صَغِيرٌ قَالَ اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ  

In our opinion it means that covenant which Allah had taken in the loins of their fathers when He said : “Am I not your Lord? They said: Yes.  

سَمِعْتُ حَمَّادَ بْنَ سَلَمَةَ يُفَسِّرُ حَدِيثَ كُلُّ مَوْلُودٍ يُولَدُ عَلَى الْفِطْرَةِ قَالَ هَذَا عِنْدَنَا حَيْثُ أَخَذَ اللَّهُ عَلَيْهِمُ الْعَهْدَ فِي أَصْلاَبِ آبَائِهِمْ حَيْثُ قَالَ { أَلَسْتُ بِرَبِّكُمْ قَالُوا بَلَى }  

The woman who buries alive her new-born girl and the girl who is buried alive both will go to Hell. This tradition has also been transmitted by Ibn Mas’ud from the Prophet (May peace be upon him) to the same effect through a different chain of narrators.  

قَالَ رَسُولُ اللَّهِ ﷺ الْوَائِدَةُ وَالْمَوْءُودَةُ فِي النَّارِ قَالَ يَحْيَى بْنُ زَكَرِيَّا قَالَ أَبِي فَحَدَّثَنِي أَبُو إِسْحَاقَ أَنَّ عَامِرًا حَدَّثَهُ بِذَلِكَ عَنْ عَلْقَمَةَ عَنِ ابْنِ مَسْعُودٍ عَنِ النَّبِيِّ ﷺ  

A man asked : where is my father, Messenger of Allah? He replied! Your father is in Hell. When he turned his back, he said : My father and your father are in Hell.  

يَا رَسُولَ اللَّهِ أَيْنَ أَبِي قَالَ أَبُوكَ فِي النَّارِ فَلَمَّا قَفَّى قَالَ إِنَّ أَبِي وَأَبَاكَ فِي النَّارِ  

The devil flows in a man like his blood.  

قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الشَّيْطَانَ يَجْرِي مِنِ ابْنِ آدَمَ مَجْرَى الدَّمِ  

Do not sit with those who believe in free will and do not address them before they address you.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ تُجَالِسُوا أَهْلَ الْقَدَرِ وَلاَ تُفَاتِحُوهُمُ الْحَدِيثَ