Origen's Commentary on the Gospel of Matthew

Then again one might inquire at what time those who are called their angels assume guardianship of the little ones pointed out by Christ; whether they received this commission to discharge concerning them, from what time “by the laver of regeneration,” through which they were born “as new-born babes, they long for the reasonable milk which is without guile,” and no longer are in subjection to any wicked power; or, whether from birth they had been appointed, according to the foreknowledge and predestination of God, over those whom God also foreknew, and foreordained to be conformed to the glory of the Christ. And with reference to the view that they have angels from birth, one might quote, “He who separated me from my mother’s womb,” and, “From the womb of my mother thou hast been my protector,” and, “He has assisted me from my mother’s womb,” and, “Upon thee I was cast from my mother,” and in the Epistle of Jude, “To them that are beloved in God the Father and are kept for Jesus Christ, being called,”—kept completely by the angels who keep them.