Hilf al-Fudul (Arabic: حلف الفضول) was an alliance or confederacy created in Mecca in the year 590 AD, to establish justice for all through collective action, especially for those who where not under the protection of any clan. Because of Muhammad’s role in its formation, the alliance plays a significant role in Islamic ethics. Because fudul commonly means “virtuous” the alliance is often translated as League of the Virtuous.
The pact, or hilf in arabic, take place at the return of the Fijar War, the battle take place in the montht of Shawwal month and the Hilf al-Fudul in the following Dhu l-Qa’da. Montgomery Watt note that the result of the war was the control of the the commercial road between Yemen and Al-Hirah by the Meccans. 
The principle of hilf was set previously by Hashim ibn Abd Manaf as a way to set up new alliances between merchants of similar power, were they Meccans or strangers, which allowed to form alliance outside of Mecca and modify the balance of power in trade inside Mecca. Hilf sometimes resulted in formation of new tribes, as it happens with the Banu Fihr.  Those transformations reshaped the traditional tribe socialisation and the social relations in Mecca. 
A Yemeni merchant from Zabid had sold some goods to al-As ibn Wa’il al-Sahmi (the father of Amr ibn al-As). Having taken possession of the goods, the Qurayshi refused to pay the agreed price, knowing that the merchant had no confederate or kinsman in Mecca whom he could count upon for help. The Yemeni merchant, instead of letting it pass, appealed to the Quraysh to see that justice was done. But due to al-As ibn Wa’il’s preeminent place among the Quraysh, they refused to help the Yemeni merchant. So the merchant went to the mountain Abi Qays to recite poems asking for justice.
Al-Zubayr ibn ‘Abd al-Muttalib, Muhammad’s uncle, is believed to have been the first to call for a pact. Muhammad, the future prophet of Islam, took part in the ‘hilf’. A few clans met in Dar al Nadwa, a building north of the Kaaba, the gathering place of the clan’s leader (malaʾ), where they decided to take defense of the Yemeni merchant and recover his loss. A meeting was hosted at the house of Abd Allah ibn Jad’an. At the meeting, various chiefs and members of tribes pledged to assist anyone who was treated unjustly, to collectively intervene in conflicts to establish justice and to defend people who were foreigners in Mecca or who were not under the protection of a clan:
To make the pact imperative and sacred, the members went into the Ka’aba and poured water into the receptacle so it flowed on the black stone. Thereupon each man drank from it. Then they raised their right hands above their heads to show they would stand together in this endeavor. The pact was written and placed inside the Ka’aba, the place where the participants believed it would be under the protection of God.
They succesfully retrieved the goods from al-As ibn Wa’il. That pact marked the beginning of some notion of justice in Mecca, which would be later repeated by Muhammad when he would preach Islam. Another aspect of the pact was that it would open up the Meccan market to Yemenite merchants, who were hitherto excluded.
The Clans involved
The following clans joined this pacte : Banu Hashim, Banu Zuhra, Banu Muthalib, Asad and Banu Taym. Montgomery Watt note the continuity with the precedent conflict for Qusay‘s succession. It opposed the same clans, grouped in hilf al Muthayyabun, to the Banu Makhzum and the Banu Sahm, who grouped in the Ahlaf. At the exception of the Banu Nawfal and the powerful ‘Abd Shams (Banu Umayya), whose success make them now closer to the Ahlaf.
For M. Watt, with the control of the trade road with the Yemen by Makhzum and ‘Abd Shams following the Fijar war, the lesser clans was going to be excluded of commerce with that country if Yemeni merchants stopped to come to Mecca. Which would explain the necessity for them to defend the Yemeni merchant. He also note that the same clans will still be in conflict until the Battle of Badr, where all Meccans leader belonged to the clans opposed to hilf al fudhul.
In the time of the first Umayyad caliph Mu’awiya, the governor of Medina al-Walid ibn Utba ibn Abi Sufyan (‘Abd Shams), who was a nephew of the caliph, committed an injustice to Husayn ibn Ali. Husayn threatened to take the case to the members of Hilf al-Fudul. As influential Meccans like Abd Allah ibn al-Zubayr (Assad), al-Miswar ibn Makhrama (al-Zuhri) and Abd al-Rahman ibn Awf (al-Taymi) swore to help Husayn in agreement with the pact, the Umayyad governor stepped back, afraid of the possible consequences. · 
- ^ Guraya, Muhammad Yusuf (1979). “JUDICIAL INSTITUTIONS IN PRE-ISLAMIC ARABIA”. Islamic Studies. 18 (4): 338. ISSN 0578-8072.
- ^ Jump up to:a b c Ibrahim, Mahmood (Aug. 1982). “Social and Economic Conditions in Pre-Islamic Mecca.” International Journal of Middle East Studies,
- ^ Jump up to:a b c Watt, W. M. Muhammad: Prophet and Statesman. Oxford University Press
- ^ Wolf, Eric R. “The social organization of Mecca and the origins of Islam.” Southwestern Journal of Anthropology 7.4 (1951)
- ^ OBAIDULLAH FAHAD (2011). “Tracing Pluralistic Trends in Sīrah Literature: A Study of Some Contemporary Scholars”. Islamic Studies. 50 (2): 221. JSTOR 41932590.
- ^ Najeebabadi, Akbar Shah. The History of Islam. Darussalam publishers. p. 101
- ^ Chelhod, Joseph (Nov. 1991). “La foi jurée et l’environnement désertique.” Arabica, 38(3): 301.
- ^ Peterson (2006),
- ^ Caetani, Annali del Islam, paragraphes 146 et 147 et notes
- ^ By M Th Houtsma. E.J. Brill’s First Encyclopaedia of Islam, 1913-1936. p. 307