Sahih Muslim Bk 19, Number 4457: Bk 32.167
https://sunnah.com/muslim:1812b
This tradition has been narrated by the game authority (Yazid b. Hurmus) through a different chain of transmitters with the following difference in the elucidation of one of the points raised by Najda in his letter to Ibn Abas: The Messenger of Allah (may peace be upon him) used not to kill the children, so thou shouldst not kill them unless you could know what Khadir had known about the child he killed, or you could distinguish between a child who would grow up to he a believer (and a child who would grow up to be a non−believer), so that you killed the (prospective) non−believer and left the (prospective) believer aside.

Sahih Muslim Bk 33, Number 6434: Bk 46.45
https://sunnah.com/muslim:2662a
Ubayy b. Ka'b reported that AUah's Messenger (may peace be upon him) said: The young man whom Khadir killed was a non−believer by his very nature and had he survived he would have involved his parents in defiance and unbelief.

Sahih Muslim Bk 33, Number 6435: Bk 46.46
https://sunnah.com/muslim:2662b
'A'isha, the mother of the believers, reported that a child died and I said: There is happiness for this child who is a bird from amongst the birds of Paradise. Thereupon Allah's Messenger (may peace be upon him) said: Don't you know that Allah created the Paradise and He created the Hell and He created the dwellers for this (Paradise) and the denizens for this (Hell)?

Sahih Muslim Bk 33, Number 6436: Bk 46.47
https://sunnah.com/muslim:2662c
'A'isha, the mother of the believers, said that Allah's Messenger (may peace be upon him) was called to lead the funeral prayer of a child of the Ansar. I said: Allah's Messenger, there is happiness for this child who is a bird from the birds of Paradise for it committed no sin nor has he reached the age when one can commit sin. He said: 'A'isha, per adventure, it may be otherwise, because God created for Paradise those who are fit for it while they were yet in their father's loins and created for Hell those who are to go to Hell. He created them for Hell while they were yet in their father's loins.

Sunan Abu Dawud Book 38, Number 4390:
https://sunnah.com/abudawud:4404
https://sunnah.com/abudawud:4405
Narrated Atiyyah al-Qurazi: I was among the captives of Banu Qurayzah. They (the Companions) examined us, and those who had begun to grow hair (pubes) were killed, and those who had not were not killed. I was among those who had not grown hair.
 

Chapter 8: PROHIBITION OF KILLING WOMEN AND CHILDREN IN WAR
Sahih Muslim Bk 19, Number 4319: Bk 32.28
https://sunnah.com/muslim:1744a
It is narrated on the authority of 'Abdullah that a woman was found killed in one of the battles fought by the Messenger of Allah (may peace be upon him). He disapproved of the killing of women and children.

Sahih Muslim Bk 19, Number 4320: Bk 32.29
https://sunnah.com/muslim:1744b
It is narrated by Ibn 'Umar that a woman was found killed in one of these battles; so the Messenger of Allah (may peace be upon him) forbade the killing of women and children.

Chapter 9: PERMISSIBILITY OF KILLING WOMEN AND CHILDREN IN THE NIGHT RAIDS, PROVIDED IT IS NOT DELIBERATE
Sahih Muslim Bk 19, Number 4321: Bk 32.30
https://sunnah.com/muslim:1745a
It is reported on the authority of Sa'b b. Jaththama that the Prophet of Allah (may peace be upon him), when asked about the women and children of the polytheists being killed during the night raid, said: They are from them.

Sahih Muslim Bk 19, Number 4322: Bk 32.31
https://sunnah.com/muslim:1745b
It is narrated by Sa'b b. Jaththama that he said (to the Holy Prophet): Messenger of Allah, we kill the children of the polytheists during the night raids. He said: They are from them.

Sahih Muslim Bk 19, Number 4323: Bk 32.32
https://sunnah.com/muslim:1745c
Sa'b b. Jaththama has narrated that the Prophet (may peace be upon him) asked: What about the children of polytheists killed by the cavalry during the night raid? He said: They are from them.