Mujahid (may Allah have mercy on him) said regarding Allah the Exalted’s statement: “Whoever kills a soul not in retaliation for another soul, or for spreading corruption in the land, it is as if he has killed all mankind” (__QUR_N__): That is, in terms of sin, it is as if he has killed all people. And he said: The meaning of “and whoever saves a life” (__QUR_N__) is: the one who has not killed anyone.
Hadith Referenceسنن سعید بن منصور / كتاب التفسير / 728