Praise be to Allah the Lord of the Worlds.
In the Noble Quran, Allah the Almighty has prescribed eight categories eligible to receive Zakah. He says, “Alms are for the poor and the needy, and those employed to administer the (funds); for those whose hearts have been (recently) reconciled (to Truth); for those in bondage and in debt; in the cause of God; and for the wayfarer: (thus is it) ordained by God, and God is full of knowledge and wisdom.”{At-Tawbah, 60}. He the Almighty has also made Zakah a constant right of those recipients where He says, "And those in whose wealth is a recognised right. For the (needy) who asks and him who is prevented (for some reason from asking)"{Al-Ma`arij/24/25}.
The poor and needy are eligible to receive Zakah, so it is permissible to give the Zakah to the poor who wants to get married and doesn`t have enough money. According to Shafie scholars, the poor is someone who doesn`t have money or job to pay for decent food, drink and accommodation, and this includes his need to get married if he wanted to preserve his chastity and eschew Zina {Adultery/fornication}. Al-Shirbini says, " According to Fatawa Ibn Al-Bizri: If the money he earns suffices only for food and accommodation, and he wanted to get married, then it is permissible to give him from the Zakah funds, because marriage is part of life expenses. This is according to the apparent opinion of the Shafie Madhab."{Moghni Al-Mohtaaj, 4/175}.
Therefore, it is permissible to give the poor from the Zakah funds to get him married by transferring that money into his possession where the charity acts as deputy for the Zakah givers and spends their money according to their conditions. If the givers haven`t stipulated a certain recipient, then the charity is permitted to act as it sees fit in line with the teachings of Sharia; similar to the Waqf administrator(Nazir Al-Waqf), the caretaker and the guardian of an orphan.
Consequently, it isn`t permissible for that charity to give any sum save for a valid reason or a necessity. Al-Shirbin (May Allah have mercy on him) says, "It isn`t permissible for the Waqf`s administrator to act save in the best interest of the Waqf itself, because he is disposing of others property similar to the orphan`s guardian."{Moghni al-Mohtajj, 10/180}. In addition, it isn`t permissible to cover wedding expenses from the Zakah funds because the latter weren`t transferred into the possession of the poor.
In addition, there are expenses, in such parties, which can`t be covered from the Zakah funds because they don`t meet the conditions of the eligible categories mentioned earlier. And Allah the Almighty knows best.