Allah, the Blessed and Exalted, says: "The sadaqat (zakah) are only for the poor, the needy, those employed to administer them, those whose hearts are to be reconciled, for freeing necks (slaves), for those in debt, in the way of Allah, and for the traveller." [Surah al-Tawbah: 60]
Imam al-Shafi'i (may Allah have mercy on him) said: "Allah Almighty made the obligation of the sadaqat firm in His Book, then He emphasised it further, saying: '(This is) an obligation from Allah.' [Surah al-Tawbah: 60]"
He said: "And it has been narrated that the Prophet (peace and blessings be upon him) said in the hadith of al-Suda'i (Sayyiduna Ziyad bin al-Harith al-Suda'i, may Allah be pleased with him): 'Indeed Allah Almighty was not pleased, concerning it (zakah), with the division of any angel brought near or any prophet sent, until He Himself divided it.'"
Sayyiduna Ziyad bin al-Harith al-Suda'i (may Allah be pleased with him), a Companion of the Prophet (peace and blessings be upon him), said: I came to the Prophet (peace and blessings be upon him) and pledged allegiance to him on Islam. Continuing the hadith, he said: Another man came to him (peace and blessings be upon him) and said: Give me some of the sadaqah too. The Messenger of Allah (peace and blessings be upon him) said: "Allah Almighty was not pleased, in the matter of the sadaqat, with the decision of His Prophet or of anyone else, until Allah Almighty Himself decided it; Allah Almighty fixed it in eight categories (portions). If you are one of them, I will give to you," or he said: "We will give you your right."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13126