مِنْ أَجْلِ ذَٰلِكَ كَتَبْنَا عَلَىٰ بَنِىٓ إِسْرَٰٓءِيلَ أَنَّهُۥ مَن قَتَلَ نَفْسًۢا بِغَيْرِ نَفْسٍ أَوْ فَسَادٍ فِى ٱلْأَرْضِ فَكَأَنَّمَا قَتَلَ ٱلنَّاسَ جَمِيعًا وَمَنْ أَحْيَاهَا فَكَأَنَّمَآ أَحْيَا ٱلنَّاسَ جَمِيعًا وَلَقَدْ جَآءَتْهُمْ رُسُلُنَا بِٱلْبَيِّنَٰتِ ثُمَّ إِنَّ كَثِيرًا مِّنْهُم بَعْدَ ذَٰلِكَ فِى ٱلْأَرْضِ لَمُسْرِفُونَ
Because of that, We decreed upon the Children of Israel that whoever kills a soul unless for a soul or for corruption [done] in the land – it is as if he had slain mankind entirely. And whoever saves one – 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. (Al-Ma’idah: 32)
Because of that, which Cain did, We decreed for the Israelites that whoever slays a soul for other than a soul, slain, or for, other than, corruption, committed, in the land, in the way of unbelief, fornication or waylaying and the like, it shall be as if he had slain mankind altogether; and whoever saves the life of one, by refraining from slaying, it shall be as if he had saved the life of all mankind – Ibn ‘Abbaas said [that the above is meant] in the sense of violating and protecting its [a soul’s] sanctity [respectively]. Our messengers have already come to them, that is, to the Israelites, with clear proofs, miracles, but after that many of them still commit excesses in the land, overstepping the bounds through disbelief, killing and the like.
Source : tafsir.learn-quran.co