Evangelical Advice

Et quicumque non receperint vos, exeuntes de civitate illa, etiam pulverem de pedibus vestris excutite in testimonium supra illos. Qualis debeat esse qui evangelizat regnum Dei, praeceptis evangelicis designatur; ut sine virga, sine pera, sine calceamento, sine pane, sine pecunia hoc est, subsidii saecularis adminicula non requirens, fideique deditus sit, et quanto minus appetat temporalia, tanto magis speret ea sibi posse suppetere. Quae possunt qui volunt ad eum derivare tractatum; ut spiritalem tantummodo locus iste formare videatur corporis exuisse, non solum potestate rejecta, contemptisque divitiis, sed etiam carnis ipsius illecebris abdicatis. Quibus primo ominim datur pacis atque constantiae generale mandatum; ut pacem fecerant, constantiam servent, hospitalis necessitudinis jura custodiant; alienum a praedictore regni coelestis astruens cursitare per domos, et inviolabilis hospitii jura mutare. Sed ut hospitii gratia deferenda censetur: ita etiam si non recipiantur, excutiendum pulverem, et egrediendum de civitate mandatur. Quo non medicoris boni remuneratio docetur hospitii, ut non solum pacem tribuamus hospitibus: verum etiam si qua eos terrenae obumbrant delicta levitatis, receptis apostolicae praedicationis vestigiis, auferantur.  Sanctus Ambrosius Mediolanensis, Evangelii secundum Lucam, Liber VI Source: Migne PL 15.1685a-b

And whoever does not receive you, go out from that city and shake off even the dust from your feet in testimony against them 1 He who evangelises for the kingdom of God should be like this, which the evangelical precepts counsel, without staff, without bag, without shoes, without bread, without money, 2 that is, not needing the support of any worldly prop, but dedicated to the faith, so that the less he desires temporal things the more he hopes that they might be supplied to him. Which they can by those who wish to learn a lesson from him, which is that the only state that is spiritual seems to be when the body has been cast off, and not only by the rejection of power and contempt for wealth, but even with the dismissal of care for one's own flesh. For this, first of all, is a commandment of peace and general steadfastness is given, that they should be peaceful and serve faithfully and guard the law of needful hospitality. A preacher of the kingdom of heaven should not be rushing around houses, and perverting the inviolable law of hospitality. But let it be reckoned that thanks should be given by the hosts, so that if they are not received, so they are ordered that they must shake off the dust and leave the city. By this it is taught that no paltry reward is given to those who are hospitable, and that we do not bestow peace alone on those who are hospitable, but even if they are shadowed by small worldly faults, such things are borne away by the reception of the Apostolic preaching.  Saint Ambrose, On The Gospel of Luke, Book 6 1 Lk 9.5 2 Lk 9.3