Because of that, We decreed upon the Children of Israel that whoever kills a soul unless for a soul1 or for corruption [done] in the land2 - it is as if he had slain mankind entirely. And whoever saves one3 - it is as if he had saved mankind entirely. And Our messengers had certainly come to them with clear proofs. Then indeed many of them, [even] after that, throughout the land, were transgressors.4
Translation: Saheeh International (English)
1 i.e., in legal retribution for murder.
2 i.e., that requiring the death penalty.
3 Or refrains from killing.
4 Heedless of Allāh's limits, negligent of their responsibilities.
لَمُسۡرِفُونَ(are) surely those who commit excesseslamus'rifūna
Tafsir
Due to Cain’s murder of his brother, I informed the Israelites that any person who kills another person for no valid reason – such as legal retribution or as punishment for causing corruption in the land by treason or waging war – it is as if he has killed all people, since he did not make a distinction between an innocent and a guilty person. Whoever refrains from killing a person whose soul I have made sacred, and regards it to be forbidden to kill such a person, it is as if he has given life to all people, because in such an action lies the safety of all people. My messengers brought to the Israelites clear signs and evidences. Despite this many of them overstepped My limits by committing sins and going against the messengers.