Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said that the Prophet (peace and blessings be upon him) "made sadaqah obligatory on eight kinds of things, then it is divided into eight portions. He (peace and blessings be upon him) made sadaqah obligatory on these things: gold, silver, camels, cows, goats, crops, grapes and dates," and this sadaqah is to be given to the eight kinds of people mentioned in this verse: "The sadaqat are only for the poor and the needy" [Surah al-Tawbah: 60].
The chain of this is weak, and the text of the Book (of Allah) is sufficient.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13127