Sahih Muslim
The Book of Jihad and Expedition (Kitab Al-Jihad wal-Siyar)
Book Number: 019 / Hadith Number: 4321
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.