Bukhari

Hadith Commentary:
A pact (halaf) refers to making an agreement and joining with another group, as was customary in the era of ignorance (jahiliyyah). Even now, however, if in times of necessity Muslims make treaties with other powers, it is evident that this will be permissible.

Hadith Commentary:
There is no contract of alliance (ʿaqd ḥilf) in Islam, because such a contract is intended to achieve mutual agreement, and Islam has already united all Muslims and joined their hearts together. Therefore, there is no need for a contract of alliance. However, from this hadith it is understood that the existence of a contract of alliance is present in Islam. In any case, the contract of alliance that is negated refers to the pact from the era of ignorance (Jahiliyyah), through which they would even become heirs of one another. Islam has abolished this. As for the contract of alliance mentioned in this hadith, it refers to the system of brotherhood (muʾākhāt), and the permissibility of a contract of alliance for mutual cooperation.

The contract of alliance of Islamic brotherhood and fraternity still exists.

Imam Nawawi rahimahullah says:
Islam has abolished the non-sharʿi contract of alliance, and that alliance and covenant is permissible because Islamic brotherhood and helping the oppressed, etc., are praiseworthy matters in Islam. Therefore, this is not abrogated.

And Allah knows best. (Fath al-Bari: 10/617)

Benefits and Issues:
It is permissible for the people of Islam and faith to make a pact or agreement based on (وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَى) [“And cooperate in righteousness and piety”].
However, agreements that are made purely on the basis of tribalism, as was the practice in the days of ignorance (jahiliyyah), have no place in Islam.
The statement of the Prophet sallallahu alayhi wa sallam: “There is no alliance (ḥilf) in Islam” also means this.

Benefit:
In the era of ignorance (Jahiliyyah), anyone could be made a confederate (halif); our Shari‘ah has prohibited this, because when someone becomes another’s confederate, he also becomes entitled to inheritance, whereas in brotherhood (mu’akhah) there is no such thing. Furthermore, it is clarified in the hadith that the confederacy (hilf) of the era of ignorance will be recognized even in the state of Islam. If someone, during the era of ignorance, made another entitled to his inheritance, and then both of them became Muslim, then considering their confederacy from the era of ignorance, the inheritance given to him will remain with him.