Praise be to Allaah.
We may divide this issue, in sha Allaah, into two parts:
Firstly: the fate of the children of the Muslims.
Secondly: the fate of the children of the kuffaar.
With regard to the first part, the fate of the children of the Muslims:
Ibn Katheer (may Allaah have mercy on him) said: With regard to the children of the believers, there is no dispute among the scholars. Al-Qaadi Abu Ya’laa ibn al-Farraa’ al-Hanbali narrated that Imaam Ahmad said: there is no dispute concerning the fact that they will be among the people of Paradise. This is what is well known among people (i.e., the majority of scholars) and this is what we are definitely sure about, in sha Allaah. (Tafseer al-Qur’aan al-‘Azeem, 3/33).
Imaam Ahmad (may Allaah have mercy on him) said: who has any doubts that the children of the Muslims will be in Paradise?!
He also said: there is no difference among them on this matter. (Haashiyat Ibn al-Qayyim ‘ala Sunan Abi Dawood, 7/83).
Imaam al-Nawawi said: the reliable Muslim scholars agreed that any Muslim child who dies will be among the people of Paradise, because he was not responsible (i.e., had not yet reached the age of account). (Sharh Muslim, 16/207).
Al-Qurtubi said: the view that they will be in Paradise is the view of the majority. And he said: some scholars denounced any dispute concerning them. (al-Tadhkirah, 2/328).
With regard to the second part, the fate of the children of the kuffaar:
The scholars differed concerning this matter, and there are several views:
That they will be in Paradise. Some of them said, they will be in al-A’raaf [a place between Paradise and Hell]. And the reason why it was said that they will be in Paradise is because this is the ultimate destiny of the people of al-A’raaf. This is the view of the majority of scholars, as reported from them by Ibn ‘Abd al-Barr in al-Tamheed, 18/96.
Their evidence (daleel):
The hadeeth of Samurah (may Allaah be pleased with him), that the Prophet (peace and blessings of Allaah be upon him) saw the children of the Muslims and the children of the Mushrikeen with Ibraaheem (peace be upon him). Narrated by al-Bukhaari, 6640.
Hasnaa’ bint Mu’aawiyyah from Bani Suraym said: my paternal uncle told me: I said, O Messenger of Allaah, who will be in Paradise? He said: Prophets will be in Paradise, martyrs will be in Paradise, infants will be in Paradise and baby girls who were buried alive will be in Paradise. Narrated by Imaam Ahmad, 5/409; classed as da’eef by al-Albaani in Da’eef al-Jaami’, 5997.
That they will be with their parents in Hell. Al-Qaadi Abu Ya’laa attributed this view to Ahmad! But Shaykh al-Islam (Ibn Taymiyah) pointed out that this was a grave error. See Haashiyat Ibn al-Qayyim ‘ala Sunan Abi Dawood, 7/87.
Their evidence (daleel):
Salamah ibn Qays al-Ashja’i said: my brother and I came to the Prophet (peace and blessings of Allaah be upon him) and said that our mother had died during the Jaahiliyyah, and that she had honoured her guests and upheld the ties of kinship, but that she had buried alive a sister of ours during the Jaahiliyyah who had not reached the age of puberty. He said: the one who was buried and the one who buried her are in Hell, unless Islam reached the one who buried the child alive and she became Muslim.
The hadeeth was classed as hasan by Ibn Katheer in al-Tafseer, 3/33, and before him by Ibn ‘Abd al-Barr in al-Tamheed, 18/120.
There are other ahaadeeth, but they are da’eef (weak).
Not giving any opinion on this matter. This is the view of Hammaad ibn Zayd, Hammaad ibn Salamah, Ibn al-Mubaarak and Ishaaq ibn Raahawayh.
Their evidence (daleel):
According to Ibn ‘Abbaas, the Prophet (peace and blessings of Allaah be upon him) was asked about the children of the mushrikeen, and he said, “Allaah knows best what they would have done.” Narrated by al-Bukhaari, 1383, and Muslim, 2660.
There is a similar hadeeth narrated by Abu Hurayrah. Narrated by al-Bukhaari, 1384, and Muslim, 2659.
Some scholars say that they (the children of the mushrikeen) will be the servants of the people of Paradise.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: there is no basis for this view. (Majmoo’ al-Fataawaa, 4/279)
I say: concerning this there was a hadeeth narrated by al-Tabaraani and al-Bazzaar, but it was classed as da’eef by the imaams – including al-Haafiz ibn Hajar in al-Fath, 3/246.
That they will be tested in the Hereafter, and whoever obeys Allaah will enter Paradise, and whoever disobeys Him will enter Hell. This is the view of the majority of Ahl al-Sunnah wa’l-Jamaa’ah, as transmitted by Abu’l-Hasan al-Ash’ari, and it is the opinion of al-Bayhaqi and many other researchers. It is also the opinion favoured by Shaykh al-Islam Ibn Taymiyah. He said that this is what is implied by the texts of Imaam Ahmad, and is the view regarded as most correct by al-Haafiz Ibn Katheer. He said: this view reconciles all the reports, and all the ahaadeeth quoted above support one another. Al-Tafseer, 3/31.
Anas said: the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Four (kinds of people) will be brought forth on the Day of Resurrection: the infant, the insane, the one who died during the Fatrah (the period between two prophets) and the very old man. All of them will speak in their own defence, then the Lord, may He be blessed and exalted, will say to a neck of Hell, ‘Come forth!’ and He will say to them, ‘I used to send Messengers to My slaves from amongst themselves. Now I am the Messenger of Myself to you. Enter this (i.e., the Fire).’ Those who are decreed to be among the doomed will say, ‘O Lord, how could we enter it when we are trying to escape it?’ And those who are decreed to be among the blessed will rush to enter it. And Allaah will say: ‘You would have been more disobedient towards My Messengers.’ So those will enter Paradise and those will enter Hell.” Narrated by Abu Ya’laa, 4224. There are corroborating reports which were mentioned by Ibn Katheer in al-Tafseer, 3/29-31.
Ibn al-Qayyim (may Allaah have mercy on him) said: this is the most reasonable of the opinions, which reconciles all the reports and brings all the ahaadeeth into harmony. On this basis, some of them will be in Paradise, as in the hadeeth of Samurah, and some of them will be in Hell, as in the hadeeth of ‘Aa’ishah. The reply of the Prophet (peace and blessings of Allaah be upon him) indicates this, as he said: “Allaah knows best what they would have done, because He created them.” It is known that Allaah does not punish anyone on the basis of what He knows, unless what He knows actually comes to pass.
The phrase “Allaah knows best what they would have done” indicates that Allaah knows what they would have done if they had lived. The ones who obey Him at the time of the test are the ones who would have obeyed Him if they had lived in this world, and those ones who disobey Him at that time are the ones who would have disobeyed Him if they had lived in this world. This indicates that He knows about what does not happen and how it would have been if it had happened. And Allaah knows best. (Haashiyat Ibn al-Qayyim ‘ala Sunan Abi Dawood, 7/87).
The ahaadeeth quoted above stating that they will either be in Paradise or in Hell do not contradict what we believe is more likely to be correct. Ibn Katheer (may Allaah have mercy on him) said: the ahaadeeth about them being tested is more specific. Whoever Allaah knows will obey Him, He puts his soul in al-Barzakh with Ibraaheem and the children of the Muslims who died in a state of Fitrah, and whoever He knows will not obey Him Him, his case rests with Allaah, and on the Day of Resurrection he will be in Hell, as is indicated in the ahaadeeth about the test and as reported by al-Ash’ari from the scholars of Sunnah. Al-Tafseer, 3/33.
The phrase “Allaah knows best what they would have done” does not mean that the Prophet (peace and blessings of Allaah be upon him) was not giving an opinion.
Ibn al-Qayyim (may Allaah have mercy on him) said: The evidence used by this group needs further examination. The answer of the Prophet (peace and blessings of Allaah be upon him) does not mean that he did not want to give an opinion; rather, he was attributing the knowledge of what they would have done if they had lived to Allaah. This was the answer to the question of how they could be with their fathers when they had no deeds in their records – which is part of the hadeeth. The Prophet (peace and blessings of Allaah be upon him) attributed the knowledge of what they would have done to Allaah; he did not say, Allaah knows best where they will be. This evidence does not support the opinion of this group. And Allaah knows best.