Let the servants of Christ then do as He commanded, or permitted them; as He fled into Egypt, let them fly from city to city, whenever any one of them is marked out for persecution; that the Church be not deserted, it will be filled by those who are not so sought after; and let these give sustenance to their fellow-servants whom they know cannot live by any other means. But when the threatening danger is common to all, Bishops, clergy, and laity, let not those who have need of aid be deserted by those whose aid they require.
Either therefore let them all pass to some stronghold, or let those who are obliged to remain, not be deserted by those whose province it is to supply their ecclesiastical needs; that they may either all live, or all suffer whatever their Master will have them to suffer.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Ep. 228