On Prayer by Tertullian
Chapter XXVI.--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 forthwith 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?