Of the Parting of Brethren
You will not dismiss a brother who has entered your house without prayer.— “Have you seen,” says Scripture, “a brother? You have seen your Lord;” — especially “a stranger,” lest perhaps he be “an angel.” But again, when received yourself by brethren, you will not make earthly refreshments prior to heavenly, for your faith will immediately be judged. Or else how will you— according to the precept — say, “Peace to this house,” unless you exchange mutual peace with them who are in the house?
Source: On Prayer (New Advent)