Islam calls for the establishment of justice among people and fairness in measure and weight.
Allah Almighty said:
{And to the people of Midian [We sent] their brother Shu‘ayb. He said, “O my people, worship Allah; you have no god other than Him. There has come to you a clear proof from your Lord. Give full measure and weight, and do not defraud people of their property, and do not spread corruption in the land after it has been set aright. That is best for you, if you are [truly] believers.} [232] Surat al-A‘rāf: 85.
{O you who believe, stand firm for Allah by bearing true testimony, and do not let the hatred of a people lead you away from justice. Be just; that is closer to righteousness. And fear Allah, for Allah is All-Aware of what you do.} [233] Surat al-Mā’idah: 8.
{Indeed, Allah commands you to return trusts to their owners, and when you judge between people, judge with justice. What an excellent exhortation from Allah to you! Indeed, Allah is All-Hearing, All-Seeing.} [234] Surat an-Nisā’: 58.
{Allah enjoins justice, kindness, and giving relatives [their dues], and He forbids shameful acts, evil deeds and oppression. He exhorts you, so that you may take heed.} [235] Surat an-Nahl: 90.
{O you who believe, do not enter any house other than your own until you ask permission and greet their dwellers. That is best for you, so that you may take heed.} Surat an-Nūr: 27.
{If you do not find anyone therein, do not enter it until you have been given permission. If you are told to go back, then go back; that is more proper for you. And Allah is All-Knowing of what you do.} [237] Surat an-Nūr: 28.
{O you who believe, if an evildoer brings you some news, verify it, lest you harm a people unknowingly, then you become regretful for what you did.} [238] Surat al-Hujurāt: 6.
{If two groups of the believers fight one another, make peace between them. If one of them transgresses against the other, fight against the transgressing group until they submit to the rule of Allah. Then if they submit, make peace between them with fairness, and be just, for Allah loves those who are just.} [239] Surat al-Hujurāt: 9.
{The believers are but brothers, so make peace between your brothers. And fear Allah, so that you may be shown mercy.} [240] Surat al-Hujurāt: 10.
{O you who believe, let not some men ridicule others, for it may be that they are better than them; nor let some women ridicule others, for it may be that they are better than them. Do not speak ill of one another, nor call one another by [offensive] nicknames. How evil is the name of wickedness after having faith! And whoever does not repent, it is they who are the wrongdoers.} [241] Surat al-Hujurāt: 11.
{O you who believe, avoid much suspicion, for some suspicions are sin. Do not spy on one another, nor backbite one another. Would any of you like to eat the flesh of his dead brother? You would surely abhor it. So fear Allah. Indeed, Allah is Accepting of Repentance, Most Merciful.} [242] Surat al-Hujurāt: 12.
The Messenger of Allah (may Allah's peace and blessings be upon him) said: "None of you is a real believer until he loves for his brother what he loves for himself.'' [243] Narrated by Al-Bukhāri and Muslim.