Gregory the Great
Catena Aurea · Lukasevangelium 10
And into whatever house ye enter, first say, Peace be to this house. And if the son of peace be there, your peace shall rest upon it: if not, it shall turn to you again. And in the same house remain, eating and drinking such things as they give; for the labourer s worthy of his hire. Go not from house to house. And into whatsoever city ye enter, and they receive you, eat such things as are set before you: And heal the sick that are therein, and say unto them, The kingdom of God is come nigh unto you. But into whatsoever city ye enter, and they receive you not, go your ways out into the streets of the same, and say, Even the very dust of your city, which cleaveth on us, we do wipe off against you: notwithstanding be ye sure of this, that the kingdom of God is come nigh unto you. But I say unto you, that it shall be more tolerable in that day for Sodom, than for that city.
(Hom. 17. in Ev.) For the peace which is offered by the mouth of the preacher shall either rest on the house, if there be any one in it predestined to life, who follows the heavenly word which he hears; or if no one be willing indeed to hear, the preacher himself shall not be without fruit, for the peace returns to him, while the Lord gives him the recompense of reward for the labour of his work. But if our peace is received, it is meet that we should obtain earthly supplies from those to whom we offer the rewards of a heavenly country. Hence it follows: And in the same house remain, eating and drinking such things as they give. Mark, that He who forbade them to carry purse and scrip, allows them to be an expense to others, and to receive sustenance from preaching.