"As Hillel the Elder had stated, whosoever destroys a soul, it is considered as if he destroyed an entire world. And whosoever that saves a life, it is considered as if he saved an entire world."
Jerusalem Talmud Sanhedrin 4:1 (22a)
"On that account: We [Allah or God] had ordained for the Children of Israel that if any one slew a person it would be as if he slew the whole world: and if any one saved a life from the people, it would be as if he saved the life of the whole world."
Islamic verses, Yuseph Ali translation 5:32