At that time: Having summoned the twelve apostles, Jesus gave them power and authority over all the devils, and to cure diseases. And so forth. Luke 9:1-6
Homily of St Ambrose, Bishop
What kind of man he should be, who preaches the kingdom of God, is clearly shown by the precepts given in the Gospel. He is to set off without staff, without packet, without shoes, without bread, without money; that is to say, not seeking the support of this world’s goods, but strong in faith, he is to consider that the less he wishes such things, the more they will abound.
Now we can, if we will, so interpret these things that this passage seems to bear a spiritual sense alone. For a man would seem to have stripped himself, as it were, of a bodily garment, when he has not only rejected power and despised wealth, but has, moreover, renounced the alluring pleasures of his own flesh.
To men such as these is given in the first place a general commandment of peace and stability, that they bring peace, that they be steady in conduct and observe the laws laid down for guests. For it does not become a preacher of the kingdom of heaven to be always going from house to house abusing the enviolate laws of hospitality.
The laws and the benefits of hospitality
But as the disciples are told to be grateful for hospitality, so also they are told when they are not received, to shake off the dust of that city and depart.
We are further taught that the reward of hospitality is no small good, since not only do we bring peace to our hosts, but if they are under the shadow of some faults of earthly vanity, they are removed when they entertain apostolic preachers.
And it is not without reason that, according to Matthew, the apostles are told to make a careful choice of the house they are to enter, that there may be no reason to change their host and thus break the ties of hospitality. But the same caution is not commanded the host, lest, in selecting his guest, his hospitality should be lessened.
The inner meaning of heavenly mystery
Yet, as in its literal sense, this passage instructs us concerning the sacred rites of hospitality, so also does it charm us with its inner meaning of heavenly mystery.
Now, when the house is chosen, a worthy host is sought for. Let us see whether this does not signify that the Church and Christ are to be preferred above all others.
What house is more fit to receive the apostolic preacher than the Church? Or who is more worthy of our choice than Christ who is accustomed to wash the feet of his guests, and does not allow those whom he has received into his house to remain there with unclean feet; but though their life is defiled, he deigns to cleanse them? This is the one host, from whom no man should depart nor seek a change of roof. And to him it is well said: “Lord, to whom shall we go? You have the words of eternal life, and we believe.”
– From: An Approved English Translation of the Breviarium Romanum, Burns & Oates, London, 1964