Luke 10:7

Or else; Since you are not appointed judges as to who are worthy and who are unworthy, eat and drink what things they offer to you. But leave to me the trial of those who receive you, unless you happen also to know that the son of peace is not there, for perhaps in that case you ought to depart.

Another virtue is added, that we should not go about easily, changing from house to house. For it follows, Go not from house to house; that is, that we should preserve a consistency in our love towards our hosts, nor lightly loose any bond of friendship.

(Hom. 17. in Ev.) 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. (ubi sup.) For now the very food which supports him is part of the wages of the labourer, as in this life the hire commences with the labour of preaching, which in the next is completed with the sight of truth. And here we must consider that two rewards are due to one work of ours, one on the journey, which supports us in labour, the other in our country, which recompenses us at the resurrection. Therefore the reward which we receive now ought so to work in us, that we the more vigorously strive to gain the succeeding reward. Every true preacher then ought not so to preach, that he may receive a reward at the present time, but so to receive a reward that he may have strength to preach. For whoever so preaches that here he may receive the reward of praise, or riches, deprives himself of an eternal reward.

See then how He taught His disciples to beg, and wished them to receive their nourishment as a reward. For it is added, For the labourer is worthy of his hire.