John Calvin on 1 Peter 4:9

9 Use hospitality, or, Be hospitable. After having generally exhorted them to love one another, he specially mentions one of the duties of love. At that time hospitality was commonly used, and it was deemed in a manner a sacred kind of humanity, as we have stated elsewhere. He then bids them mutually to exercise it, so that no one might require more from others than what he himself was prepared to render. He adds, without murmurings, for it is a rare example that one spends himself and his own on his neighbor without any disparaging reflection. Then the Apostle would have us to show kindness willingly and with a cheerful mind.