Killing Enemies’ Children is Forbidden
Al-Aswad ibn Sari' (May Allah be Pleased with him) reported that, on the Battle of Hunain, the Prophet (PBUH) dispatched a group of soldiers who fought against the assaulting non-Muslims and, consequently, killed some of their children. Upon their return, the Prophet asked, "Why did you kill the children?" They replied, "O messenger of Allah, they are children of polytheists. The Prophet thereupon said, "The best among you today are the children of idolaters. Do not kill the children! [repeating it twice]."