Hadith 127:5
Isma'il narrated to us, he said: Yunus informed us, from al-Hasan, from al-Aswad ibn Sari', who said: I came to the Messenger of Allah, may Allah bless him and grant him peace, and I went on a military expedition with him, and I obtained a mount. The people killed on that day until they even killed the children—and he said once: the offspring. That reached the Messenger of Allah, may Allah bless him and grant him peace, so he said: "What is the matter with some people who exceeded the limits in killing today, until they killed the offspring?" A man said: "O Messenger of Allah, they are only the children of the polytheists." He said: "Are not the best of you the children of the polytheists?" Then he said: "Beware, do not kill offspring. Beware, do not kill offspring." He said: "Every soul is born upon the natural disposition (fitrah), until its tongue expresses it, then its parents make it a Jew or make it a Christian."
حدثنا إسماعيل، قال: أخبرنا يونس، عن الحسن، عن الأسود بن سريع، قال: أتيت رسول الله صلى الله عليه وسلم، وغزوت معه فأصبت ظهرا، فقتل الناس يومئذ حتى قتلوا الولدان - وقال مرة: الذرية - فبلغ ذلك رسول الله صلى الله عليه وسلم فقال: " ما بال أقوام جاوزهم القتل اليوم حتى قتلوا الذرية " فقال رجل: يا رسول الله، إنما هم أولاد المشركين، فقال: " ألا إن خياركم أبناء المشركين " ثم قال: " ألا لا تقتلوا ذرية، ألا لا تقتلوا ذرية " قال: " كل نسمة تولد على الفطرة، حتى يعرب عنها لسانها، فأبواها يهودانها وينصرانها "