(2) and he lifted up his eyes and looked, and, lo, three men stood over against him; and when he saw them, he ran to meet them from the tent door, and bowed down to the earth, (3) and said: ‘My lord, if now I have found favour in thy sight, pass not away, I pray thee, from thy servant. (4) Let now a little water be fetched, and wash your feet, and recline yourselves under the tree. (5) And I will fetch a morsel of bread, and stay ye your heart; after that ye shall pass on; forasmuch as ye are come to your servant.’ And they said: ‘So do, as thou hast said.’ (6) And Abraham hastened into the tent unto Sarah, and said: ‘Make ready quickly three measures of fine meal, knead it, and make cakes.’ (7) And Abraham ran unto the herd, and fetched a calf tender and good, and gave it unto the servant; and he hastened to dress it. (8) And he took curd, and milk, and the calf which he had dressed, and set it before them; and he stood by them under the tree, and they did eat. (9) And they said unto him: ‘Where is Sarah thy wife?’ And he said: ‘Behold, in the tent.’ (10) And He said: ‘I will certainly return unto thee when the season cometh round; and, lo, Sarah thy wife shall have a son.’ And Sarah heard in the tent door, which was behind him.— (11)
Mishnah Sanhedrin 4:5"It was for this reason that man was first created as one person [Adam], to teach you that anyone who destroys a life is considered by Scripture to have destroyed an entire world; any any who saves a life is as if he saved an entire world." And also, to promote peace among the creations, that no man would say to his friend, "My ancestors are greater than yours."
Adam Yachid -The rabbinic concept that one human being was originally created so that no person could say "my father is greater than your father." In other words, every human being is unique and inherently precious (Mishnah Sandhedrin 4:5)