The Prophet ﷺ said, "If you possess two hundred dirhams and a year passes over them, then five dirhams are due on them. Nothing is due on you regarding gold until you possess twenty Dinars. If you possess twenty Dinars and a year passes over them, then half a Dinar is due on them, and whatever exceeds that is calculated accordingly."
عن النبي ﷺ قال: فإذا كانت لك مائنا درهم وحال عليها الحول ففيها خمسة دراهم وليس عليك شيء يعني في الذهب حتى يكون لك عشرون دينارا فإذا كان لك عشرون دينارا وحال عليها الحول ففيها نصف دينار فما زاد فبحساب ذلك.
Abu Dawud (1573) narrated it from Sulayman bin Dawud Mahri, who said, Ibn Wahb told us, Jareer bin Hazim told me, and he named another narrator, from Abu Ishaq, from Asim bin Damra and Harith Awar, from Ali bin Abu Talib, and he related it. Its chain is hasan because of Asim bin Damra, who is truthful (saduq). Harith Awar also transmitted it alongside him, though there is well known discussion about him. For a detailed examination of its sources, see the chapter "There is no zakat due on wealth until a full year has passed over it." Here I will add the following.This hadith was recorded by Ibn Hazm in al-Muhalla (6/84), where he criticized it on account of Harith and others, but then he corrected himself, saying, "We then reconsidered, and found that the hadith of Jareer bin Hazim is a sahih connected report, which cannot be contradicted. The criticism directed at it, namely that Asim bin Damra, or Abu Ishaq, or Jareer confused matters in Harith's chain by making Asim's report disconnected, is a baseless assumption that is not admissible. It does not concern us whether Harith shared this report with Asim, nor whether someone reported it in disconnected form, nor does Zuhayr's doubt about it matter at all. Jareer is reliable, so accepting what he transmitted as connected is required. And success comes from Allah." Al-Muhalla (6/91).There are other hadiths on this subject. Among them is what Ibn Majah (1791) narrated from Bakr bin Khalaf and Muhammad bin Yahya, who both said, Ubaydullah bin Musa told us, saying, Ibrahim bin Ismail informed us, from Abdullah bin Waqid, from Ibn Umar and Ayesha, that the Prophet ﷺ used to take half a dinar from every twenty dinars and above, and one dinar from every forty dinars. This report contains Ibrahim bin Ismail, who is Ibn Mujammi Ansari, Abu Ishaq Madani, and the scholars unanimously judge him daif. Daraqutni (1896) also narrated it through his route.Among them also is what Daraqutni (1902) narrated with his chain from Ibn Abu Layla, from Abdul-Kareem, from Amr bin Shuayb, from his father, from his grandfather, from the Prophet ﷺ, who said, and he related the hadith. It states, "There is nothing due on less than twenty mithqals of gold, and nothing due on less than two hundred dirhams." Abdul-Kareem here is Ibn Abu Makharaq, Abu Umaya Muallim, and the scholars unanimously judge him daif. The one who transmitted from him, Ibn Abu Layla, is Muhammad bin Abdul-Rahman bin Abu Layla, who is "truthful but very weak in memory," as stated in al-Taqrib.There are other hadiths on this subject as well, and all of them contain some point of criticism, but some of them reinforce and strengthen others, and this is the position the majority adopted.Malik said in Muwatta, "The established practice among us, upon which there is no disagreement, is that zakat becomes obligatory on twenty dinars of gold coin, just as it becomes obligatory on two hundred dirhams."Shafii said in al-Risala (p. 192), "The Messenger of Allah ﷺ imposed an obligatory charity on silver currency, and the Muslims took up the same obligation regarding gold as well, either based on a report from the Prophet ﷺ that did not reach us, or by analogy, since gold and silver were the currency people used, which they stored up and accepted as prices in their transactions in various lands, both before and after Islam."The Hanafis said, as recorded in Usul Sarakhsi (p. 110), "There is no disagreement among our scholars, both the earlier and the later ones, that the statement of a single companion is authoritative evidence in matters where analogy has no role in determining the ruling, such as fixed measures that cannot be known through reasoning." Among these he mentioned the zakat on gold.Tawus, Zuhri, Ataa, and Sulayman bin Harb disagreed with them on this point, saying that the minimum threshold for gold is determined by valuing it against silver. Hasan Basri said that its threshold is forty dinars.The correct view is the one held by the majority, and after this disagreement they agreed that the threshold for gold is twenty dinars, which today is equivalent to 85 grams, though some say 92 grams. As for the threshold for silver, it is equivalent to 595 grams.Whoever holds paper currency should value it against silver, since this serves the interests of the poor. When its value reaches the threshold of silver, and a full year has passed over it, zakat becomes obligatory on it.