Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) relates that the Prophet (peace and blessings be upon him) said: "Every child is born upon the fitrah (natural disposition); his parents make him a Jew or a Christian."
Al-Bazzar recorded it; its chain contains more than one narrator whom I do not know.
(Allamah al-Haythami says:) I say: the hadith of Sayyiduna al-Aswad bin Sari' (may Allah be pleased with him) and others has already passed, concerning the prohibition of killing women and children during war.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب القدر / 11949