Jamieson, Fausset and Brown on 1 Peter 4:9

9. (Ro 12:13; He 13:2.) Not the spurious hospitality which passes current in the world, but the entertaining of those needing it, especially those exiled for the faith, as the representatives of Christ, and all hospitality to whomsoever exercised from genuine Christian love.

without grudging--Greek, "murmuring." "He that giveth, let him do it with simplicity," that is open-hearted sincerity; with cordiality. Not secretly speaking against the person whom we entertain, or upbraiding him with the favor we have conferred in him.