Flavius Josephus,
Antiquities of the Jews
“ That accordingly God said to him, that "because the Amalekites did the Hebrews a great deal of mischief while they were in the wilderness, and when, upon their coming out of Egypt, they were making their way to that country which is now their own, I enjoin thee to punish the Amalekites, by making war upon them; and when thou hast subdued them, to leave none of them alive, but to pursue them through every age, and to slay them, beginning with the women and the infants, and to require this as a punishment to be inflicted upon them for the mischief they did to our forefathers ”
