Ambrose of Milan — as excerpted in the Catena Aurea on Matthew 10:11-15

“(in Luc. 9:5.) The Apostles are not to choose carelessly the house into which they enter, that they may have no cause for changing their lodging; the same caution is not enforced upon the entertainer, lest in choosing his guests, his hospitality should be diminished. When ye enter a house, salute it, saying, Peace be to this house.”