The Qur'ān says, “Indeed, God enjoins justice and kindness.” (16:90) Given that the context of this verse pertains to the responsibilities of human beings toward their society, the term ‘justice’ should be interpreted as ‘social justice’. Thus, God has ordered human beings to uphold justice.
'Allāma Ṭabāṭabā'ī has said that social justice denotes treating each member of society in accordance with their merit and ensuring everyone receives their rights. This social quality is an obligation that responsible individuals must observe [1]

The establishment of social justice is one of the most important teachings of divine prophets ('a). Hence they strived to explain its essence and scientific principles, inculcate its spirit within humanity, and compel its acceptance as a cornerstone upon which earthly life depends. Anyone with basic knowledge of religious teachings understands that the establishment of social justice enlivens God's religion. 

Thus, until justice prevails, true religion remains incomplete. Similarly, until universal social justice takes root, the fulfillment of religious and legal obligations remain unattained. [2]

The absence of social justice historically has been the cause of most revolutions. Noble-minded reformers have consistently started their movements with the of establishing social justice and eradicating discrimination. The Prophet (ṣ) said that “Justice in social struggle is like a guardian shield which protects people from oppression; and it is like a stable paradise that perpetually bestows its blessings” [3]

Although it is necessary for everyone to respect one another's rights, it is more important for a leader [to respect human rights]. In this regard, Imām 'Alī ('a) told his commanders that neglecting people's rights equates to ruin [4]. Additional, Imām Riḍā ('a) said that the Household (Ahl al-Bayt) of the Prophet (ṣ) are guardians and protectors of the believers' rights [5]

However, it is not solely leaders who must foster social justice; Islām has said both leaders and followers possess rights. Social justice can only thrive when everyone's rights are upheld. Imām 'Alī ('a) said that mutual respect between leaders and followers results in the elevation of righteousness, the revelation of religious principles, and the solidification of just characteristics.[6]

Characteristics of Social Justice

1.    Meritocracy

One of the most important characteristics of social justice is meritocracy, which means entailing the assignment of roles and responsibility based on individual merit. Justice mandates that the most qualified individuals are given precedence for opportunities and higher positions. 

Imām 'Alī ('a) instructed Mālik Ashtar to appoint individuals to different positions in accordance with their merit (Nahj al-Balāgha, letter to Malik Ashtar). The Prophet (s) emphasized that it is treachery to appoint less qualified people to positions of authority [7]

2.    Prioritizing the Rights of the Impoverished and Needy

Another characteristic of social justice is paying attention to the rights of the poor and needy. Injustice is a contributing factor to poverty, which in turn breeds various hardships. Luqman said that of all the bitterness he had encountered, poverty was the harshest. The Prophet (s) said that poverty, pain, enmity, and fire are never trivial [8], and that poverty represents a significant form of death [9]

These reports show that leaders have heavy responsibilities, because the poor need justice more than other people. 

3.    Respecting People's Rights 

When oppression becomes prevalent in society, leaders should not merely distance themselves from it; they ought to stand up and fight for the rights of the oppressed. In fact, all individuals must resist remaining silent when others endure oppression, as passivity equates to complicity in oppression.

Furthermore, not only oppression destroys everything, including culture, economics, wisdom, ability, talent, innovation, etc. but also it is the biggest obstacle to establish justice within society. Imam 'Alī ('a) asserted that ending oppression is a prerequisite for justice.

4.    Equity and Impartiality

It has been reported that one day a rich man and a poor man were sitting next to each other. The rich man pulled his face at the poor man and adjusting his clothes. Observing this the Prophet (ṣ) asked the rich man “Are you afraid that some of his poverty will be transmitted to you?” [10]

The Prophet (s), both in words and acts, paid attention to this important characteristic. For example, when a woman from the Banī Makhzūm tribe committed theft and the people asked the Prophet (s) to judge, her family, who were still influenced by the customs of the class system, considered execution of punishment to be shameful for their aristocratic family. As a result, they started looking for ways to prevent the punishment. To this end, they coerced Usama ibn Zayd, whom the Prophet (s) held in deep affection, to intercede with the Prophet (s) and halt the punishment. However, scarcely had Usama begun to speak when the Prophet (s) grew angry and said no one should stop him from implementing God's laws. Usama promptly sought forgiveness. Later that day, the Prophet (s), aiming to dispel any perception of favoritism, addressed the incident in a speech. He said “Throughout history, tribes and nations declined and vanished due to favoritism in justice’s administration. When both an aristocrat and a commoner committed the same crime, they would punish the commoner while granting impunity to the aristocrat. I swear by the God in whose hands hold my life that I shall spare no one from punishment, regardless of their social standing, whether high or low” [11]

On a different occasion, when Umm Hānī, Imām Alī's sister, went to see him, the Imam gave her twenty dirhams. When she asked her non-Arab bondswoman about her received amount, the female slave said she had also been given twenty dirhams. Incensed by this equality, Umm Hānī confronted her brother, Imam Ali, in protest. In response, the Imam sent her back with these words: “Go back, and may God forgive you. In the Book of God, we have not found any preference for Ishmael over Isaac” [12]

5.    Distinction between the Benevolent and the Malevolent

A leader must avoid treating benevolent and malevolent individuals equally, as this engenders injustice. Imām Alī ('a) instructed Mālik Ashtar to avoid treating benevolent and malevolent individuals equally, because doing so could discourage the benevolent and embolden the malevolent. Instead, everyone should be rewarded according to their deeds.[13]
   

       
          references 

1. (Al-Mīzān fī Tafsīr al-Qur'ān, vol. 24, pp. 243-246).
2. (Al-Ḥayāt, vol. 2, p. 97).
3. (al-Ḥadīth – Riwayāt-e Tarbiyyatī, vol. 2, p. 265). 
4. (Nahj al-Balāgha, letter no. 79)
5. (Musnad al-Imām al-Riḍā, ('a), vol. 1, p. 136). 
6. (Nahj al-Balāgha, sermon no. 216). 
7. (Al-Ta'ajub, p. 59).
8. (Nahj al-Faṣāha, saying no. 252)
9. (Nahj al-Balāgha, saying no. 163).
10. (Majmu'at Waram, vol. 1, p. 214).
11. (Ṣaḥīḥ Bukhārī, vol. 5, p. 152).
12. (Biḥār al-Anwār, vol. 40, p. 106).
13. (Nahj al-Balāgha, letter no. 53). 

In answering questions about singing in Islam, we cannot say that singing is completely forbidden (Haram) in Islam. Like any other issue, we have to find out what kind of singing is allowed (Halal) and that if there is a prohibition, what is that makes it forbidden (Haram)?

What Makes Singing in Islam Forbidden (Haram)?

In deriving the ruling of singing from the Quran, jurists usually refer to two main verses:

“Among the people is he who buys diversionary talk that he may lead [people] astray from Allah’s way without any knowledge, and he takes it in derision. For such, there is a humiliating punishment” (31:6).

Some interpreters have taken the phrase “diversionary talk” (Lahw al-hadith) as any sort of speech that deviates people’s minds from the righteous way and attracts the concentration of people to an unjust saying. Jurists have expanded the unjust saying to any sort of expression of mind which may contain poetry or singing or music [2].

Also, it is said in another verse: “So avoid the abomination of idols, and avoid false speech …” (22:30).

In the interpretation of “false speech” (Qowl al-zur) in this verse, it is said that a false statement is any word that deviates people from the righteous way and remembrance of God [3].

When jurists want to define the forbidden (Haram) singing in Islam, they use the term “ghina”.  In Islamic jurisprudence, singing is not forbidden (Haram) unless it is known to be ghina.

What is Ghina?

Ghina is the voice of a human, which is produced in a rise and fall pattern to create the effect of rapture that is suitable for frivolous and carouse gatherings. It is forbidden (Haram) to engage in this type of singing; as well as listening to it, even if it does not lead to rapture in the listener [4].

Any kind of singing that deviates a person from a moderate mood (may it be happy or sad) is referred to as ghina. The most visible sign of this deviation from a moderate mood is when the person loses his self-control; like the feeling that occurs to man after drinking wine. Islam has always prevented Muslims from being stuck in such moods.

Gatherings of merrymaking and sin are those kinds of gatherings that are formed for singing, dancing, debauchery, and sensuality.

Also, there might be some songs that do not deviate one from his/her moderate mood but are common for gatherings of merrymaking and sin. Those are also known as ghina.

Have you ever seen in some concerts, how the audience lose their mind and apart from dancing or crying with the song, they shout or faint out of rapture? This kind of singing is ghina, and those sorts of gatherings are referred to as gatherings of merrymaking and sin. Any kind of singing that changes the normal and rational mood of a person is ghina [5].

Some Hints to Recognize Ghina

Ghina is the type of song that is branded for amusement gatherings and parties.
Ghina is related to the type of song; meaning that if the lyrics of a song convey positive messages to the listener but the music of the song is jaunty, it makes that music forbidden (Haram) [6].
Ghina is when the lyrics of a song are about describing the beauties of a woman (whether physical or erotic description), or it has been written about wine, or dance or other prohibited (Haram) things in Islam [7].
Ghina is any song that changes the mood of the listener; makes him/her either happy or sad; any music or song that makes a gap between the present moods of the listener with his/her “real self” and weakens the control of the person over her speech or behavior.
Ghina is the sort of song that has such hopeless content, which destroys the positive motivations of the listener.
Ghina is any kind of song that by content, lyrics, or the specific sound of the musical instrument can arouse sexual temptation.

What Sort of Singing Is Lawful (Halal) in Islam?

Having mentioned the criteria of forbidden (Haram) singing, we can say that those songs which do not contain the conditions mentioned above are lawful (Halah).

Overall, if the listener maintains that as per common view they are not enraptured, there is no problem in listening to the songs (with or without music). Thus, neither the intention of the singer nor the content have anything to do with this ruling [8].

Listening to Women or Children Singing in Islam

In the matter of listening to a woman reciting poetry and other material with rising and falling her voice to the accompaniment of music, if the vocalization does not amount to ghina, listening to it is not driven by lust, and does not lead to a bad consequence, there is no problem in listening to it for women. If a woman’s signing is sexually exciting or listening to it leads to vile consequences, it is not allowed to listen to it at all. [9]

Regarding women’s singing to be heard by men, if it is not ghina and is not intended for questionable purposes or does not lead to vile consequences, as long as it is not sexually erotic, it is not forbidden (Haram). But as it often happens that listening to the beautiful voice of women is joyful for men, it is better if women do not sing for men and for men not to listen to women singing.

References:

1. Ma’aref and Ma’arief, vol. 8, p. 283
2. singing in Islam
3. Rouhollah Khaleghi, An overview of music, p.4
4. muslim singing
5. Sayyid Mujtaba Husseini, Questions and Answers by Students (Rules regarding Music), pg. 40-42
6. Art from the point of view of the supreme leader, p. 32-4
7. Tafsir –e Qartabi, vol. 7, p. 5136
8. singer 
9. Are Muslim allowed to sing?