Hilary of Poitiers

Figuratively, The Lord teaches us not to enter the houses or to mix in the acquaintance of those who persecute Christ, or who are ignorant of Him; and in each town to enquire who among them is worthy, i. e. where there is a Church wherein Christ dwells; and not to pass to another, because this house is worthy, this host is our right host. But there would be many of the Jews who would be so well disposed to the Law, that though they believed in Christ because they admired His works, yet they would abide in the works of the Law; and others again who, desiring to make trial of that liberty which is in Christ, would feign themselves ready to forsake the Law for the Gospel; many also would be drawn aside into heresy by perverse understanding. And since all these would falsely maintain that with them only was Catholic verity, therefore we must with great caution seek out the house, i. e. the Church.