Mishna, Sanhedrin 4:5 - Part 2

Therefore, humans were created singly, to teach you that whoever destroys a single soul [of Israel], Scripture accounts it as if he had destroyed a full world; and whoever saves one soul of Israel, Scripture accounts it as if she had saved a full world. And for the sake of peace among people, that one should not say to his or her fellow, "My parent is greater than yours;" and that heretics should not say, "There are many powers in Heaven." Again, to declare the greatness of the Holy One, blessed be God, for one stamps out many coins with one die, and they are all alike, but the King, the King of kings, the Holy One, blessed be God, stamped each person with the seal of Adam, and not one of them is like his or her fellow. Therefore each and every one is obliged to say, "For my sake the world was created." And lest you say, "What do we need with this trouble?" Has it not already been said, "He being a witness, whether he has seen or known, if he does not utter it..." (Leviticus 5:1). And should you say, "What need is there for us to be responsible for the blood of this one?" Surely it is said, "And when the wicked perish, there is joy" (Proverbs 11:10). [Moreshet translation. Edited for gender neutrality] (This text has parallels in Jerusalem Talmud, Sanhedrin 4:22, Babylonian Talmud Sanhedrin 37a, Psikta Zutra Bereshit 1)