Hebrews 13:2 reminds us, “Do not neglect to show hospitality to strangers, for by doing that some have entertained angels without knowing it.” This is exactly what happens to Abraham in Genesis 18. Abraham is sitting out the heat of the day in front of his tent when he sees three men nearby. He doesn't hesitate for a moment. He jumps up and invites them to wash their feet and rest while he prepares a meal.
Abraham has no idea who these three men really are. They could be saints or thieves, but he makes no judgment. Rather, he sees them as three tired travelers who need the rest and refreshment that he can provide, and he is quick to set himself at their service, no matter who they are.
Abraham moves quickly, telling Sarah to bake some cakes and ordering a servant to prepare a calf. When the meal is ready, he does not share it with them. Rather he assumes the role of a servant, standing near the men to make sure they have everything they need while they enjoy the food.
Are these three men angels? The three Persons of the Blessed Trinity? Angels representing the three Persons of the Blessed Trinity? We don't know, and neither does Abraham, but he provides the very best for then. In turn, they bring him the very best of news. By this time next year, God will have fulfilled His promise to Abraham. Abraham and Sarah will have a baby boy. Now there's a fine reward for a little bit of hospitality!