Human Beings Should Respect the Sanctity of Other Human Beings
Allah says,
مِنْ أَجْلِ ذَلِكَ
Because of that,
Allah says, because the son of Adam killed his brother in transgression and aggression,
كَتَبْنَا عَلَى بَنِي إِسْرَايِيلَ
We ordained for the Children of Israel...,
meaning, We legislated for them and informed them,
أَنَّهُ مَن قَتَلَ نَفْسًا بِغَيْرِ نَفْسٍ أَوْ فَسَادٍ فِي الَارْضِ فَكَأَنَّمَا قَتَلَ النَّاسَ جَمِيعًا وَمَنْ أَحْيَاهَا فَكَأَنَّمَا أَحْيَا النَّاسَ جَمِيعًا
that if anyone killed a person not in retaliation of murder, or (and) to spread mischief in the land - it would be as if he killed all mankind, and if anyone saved a life, it would be as if he saved the life of all mankind.
The Ayah states, whoever kills a soul without justification -- such as in retaliation for murder or for causing mischief on earth -- will be as if he has killed all mankind, because there is no difference between one life and another.
وَمَنْ أَحْيَاهَا
(and if anyone saved a life...),
by preventing its blood from being shed and believing in its sanctity, then all people will have been saved from him, so,
أَحْيَا النَّاسَ جَمِيعًا
(it would be as if he saved the life of all mankind).
Al-Amash and others said that Abu Salih said that Abu Hurayrah said,
"I entered on Uthman when he was under siege in his house and said, `I came to give you my support. Now, it is good to fight (defending you) O Leader of the Faithful!'
He said, `O Abu Hurayrah! Does it please you that you kill all people, including me?'
I said, `No.'
He said, `If you kill one man, it is as if you killed all people. Therefore, go back with my permission for you to leave. May you receive your reward and be saved from burden.'
So I went back and did not fight."'
Ali bin Abi Talhah reported that Ibn Abbas said,
"It is as Allah has stated,
مَن قَتَلَ نَفْسًا بِغَيْرِ نَفْسٍ أَوْ فَسَادٍ فِي الَارْضِ فَكَأَنَّمَا قَتَلَ النَّاسَ جَمِيعًا وَمَنْ أَحْيَاهَا فَكَأَنَّمَا أَحْيَا النَّاسَ جَمِيعًا
if anyone killed a person not in retaliation of murder, or (and) to spread mischief in the land - it would be as if he killed all mankind, and if anyone saved a life, it would be as if he saved the life of all mankind.
Saving life in this case occurs by not killing a soul that Allah has forbidden.
So this is the meaning of saving the life of all mankind, for whoever forbids killing a soul without justification, the lives of all people will be saved from him."
Similar was said by Mujahid;
وَمَنْ أَحْيَاهَا
(And if anyone saved a life...),
means, he refrains from killing a soul.
Al-`Awfi reported that Ibn Abbas said that Allah's statement,
فَكَأَنَّمَا أَحْيَا النَّاسَ جَمِيعًا
(it would be as if he killed all mankind...) means,
"Whoever kills one soul that Allah has forbidden killing, is just like he who kills all mankind."
Sa`id bin Jubayr said,
"He who allows himself to shed the blood of a Muslim, is like he who allows shedding the blood of all people. He who forbids shedding the blood of one Muslim, is like he who forbids shedding the blood of all people."
In addition, Ibn Jurayj said that Al-A`raj said that Mujahid commented on the Ayah,
فَكَأَنَّمَا قَتَلَ النَّاسَ جَمِيعًا
(it would be as if he killed all mankind),
"He who kills a believing soul intentionally, Allah makes the Fire of Hell his abode, He will become angry with him, and curse him, and has prepared a tremendous punishment for him, equal to if he had killed all people, his punishment will still be the same."
Ibn Jurayj said that Mujahid said that the Ayah,
وَمَنْ أَحْيَاهَا فَكَأَنَّمَا أَحْيَا النَّاسَ جَمِيعًا
(and if anyone saved a life, it would be as if he saved the life of all mankind) means,
"He who does not kill anyone, then the lives of people are safe from him."
Warning Those who Commit Mischief
Allah said,
وَلَقَدْ جَاء تْهُمْ رُسُلُنَا بِالبَيِّنَاتِ
And indeed, there came to them Our Messengers with Al-Bayyinat,
meaning, clear evidences, signs and proofs.
ثُمَّ إِنَّ كَثِيرًا مِّنْهُم بَعْدَ ذَلِكَ فِي الَارْضِ لَمُسْرِفُونَ
even then after that many of them continued to exceed the limits in the land!
This Ayah chastises and criticizes those who commit the prohibitions, after knowing that they are prohibited from indulging in them.
The Jews of Al-Madinah, such as Banu Qurayzah, An-Nadir and Qaynuqa, used to fight along with either Khazraj or Aws, when war would erupt between them during the time of Jahiliyyah. When these wars would end, the Jews would ransom those who were captured and pay the blood money for those who were killed. Allah criticized them for this practice in Surah Al-Baqarah,
وَإِذْ أَخَذْنَا مِيثَـقَكُمْ لَا تَسْفِكُونَ دِمَأءِكُمْ وَلَا تُخْرِجُونَ أَنفُسَكُمْ مِّن دِيَـرِكُمْ ثُمَّ أَقْرَرْتُمْ وَأَنتُمْ تَشْهَدُونَ
ثُمَّ أَنتُمْ هَـوُلَاءِ تَقْتُلُونَ أَنفُسَكُمْ وَتُخْرِجُونَ فَرِيقًا مِّنكُم مِّن دِيَـرِهِمْ تَظَـهَرُونَ علَيْهِم بِالاِثْمِ وَالْعُدْوَنِ وَإِن يَأْتُوكُمْ أُسَـرَى تُفَـدُوهُمْ وَهُوَ مُحَرَّمٌ عَلَيْكُمْ إِخْرَاجُهُمْ أَفَتُوْمِنُونَ بِبَعْضِ الْكِتَـبِ وَتَكْفُرُونَ بِبَعْضٍ فَمَا جَزَاءُ مَن يَفْعَلُ ذلِكَ مِنكُمْ إِلاَّ خِزْىٌ فِي الْحَيَوةِ الدُّنْيَا وَيَوْمَ الْقِيَـمَةِ يُرَدُّونَ إِلَى أَشَدِّ الّعَذَابِ وَمَا اللَّهُ بِغَـفِلٍ عَمَّا تَعْمَلُونَ
And (remember) when We took your covenant (saying);Shed not your (people's) blood, nor turn out your own people from their dwellings. Then, (this) you ratified and (to this) you bear witness.
After this, it is you who kill one another and drive out a party of your own from their homes, assist (their enemies) against them, in sin and transgression. And if they come to you as captives, you ransom them, although their expulsion was forbidden to you. Then do you believe in a part of the Scripture and reject the rest Then what is the recompense of those who do so among you, except disgrace in the life of this world, and on the Day of Resurrection they shall be consigned to the most grievous torment. And Allah is not unaware of what you do. (2;84-85)
The Punishment of those Who Cause Mischief in the Land
Allah said next