I found this in a commentary:

Regarding hospitality: "This widely praised virtue in that day was practically a social obligation for the householder. It also became a mark of Christian behavior (Rom 12:13; 1 Pet 4:9). What sometimes passes for hospitality today (the entertainment of friends and church members, often with the expectation of a return invitation) is a rather dim reflection of the New Testament concept. The practice of hospitality among Christians was often urgent, sacrificial and risky: urgent because Christians might be forced from homes or jobs with no one to turn to but fellow Christians; sacrificial because material goods were often in short supply; risky because to associate oneself with those who had been forced out meant to identify with their cause. Thus hospitality required sacrificial sharing and stretching. It was a very practical expression of love, not a source of entertainment. While the practice of hospitality had primarily the needs of believers in mind, there is no reason that it could not be a way of showing concern for unbelievers."