Library Theophilus of Antioch To Autolycus
Book 3, Chapter 10: Of Humanity to Strangers.
Since therefore they were strangers in the land of Egypt, being by birth Hebrews from the land of Chaldæa — for at that time, there being a famine, they were obliged to migrate to Egypt for the sake of buying food there, where also for a time they sojourned; and these things befell them in accordance with a prediction of God — having sojourned, then, in Egypt for 430 years, when Moses was about to lead them out into the desert, God taught them by the law, saying, You shall not afflict a stranger; for you know the heart of a stranger: for yourselves were strangers in the land of Egypt.
Exodus 22:21
English translation by Marcus Dods, in Ante-Nicene Fathers, Vol. II (eds. Alexander Roberts and James Donaldson; Buffalo: Christian Literature Publishing Co., 1885). Public domain. Digital text via New Advent Church Fathers.