Through their hospitality, Abraham and Sarah taught their guests to thank the Creator of the world for their food.

Abraham would receive the passersby. After they would eat and drink, he would tell them: Recite a blessing. They would say to him: What should we say? Abraham would tell them to say: Blessed is the eternal God, whose food we have eaten. If the guest would accept it upon himself and recite the blessing, he would eat, drink, and go. If he would not accept it upon himself, Abraham would say to him: Give me what you have [in exchange for what you consumed]. The guest would say: What claim do you have on me? Abraham would say to him: I supplied you with one jug of wine for ten polar, one litra of meat for ten polar, and one loaf of bread for ten polar. Who would give you wine in the wilderness? Who would give you meat in the wilderness? Who would give you a loaf in the wilderness? Once the guest would see all this trouble that [Abraham] was causing him, he would say: Blessed is the eternal God whose food we have eaten. And that is what is written with regard to Abraham: “To perform charity and justice” (Genesis 18:19). Initially, charity, and ultimately, justice. Initially, charity…justice: Initially, he followed the path of charity and kindness; but ultimately, he resorted to a resolute demand, employing the quality of justice. (Bereshit Rabba 49)