Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.049A.

Rikaz might be found in the following places:

1. In a barren land, a land of unknown ownership, or in an intractable road, or ruined village. In that case, khums has to be paid, and the one who found it may keep the other four-fifths for himself. This is based on a report from an-Nasa’i on the authority of ‘Amr ibn Shu’aib from his father and from his grandfather, who said that when the Messenger of Allah, upon whom be peace, was asked about a lucky find (al-luqatah), he responded: “For anything along a tractable road or in an inhabited village, its ownership is determined by established custom. If the owner claims it, it is his. However, when an item is found in an intractable road or in an uninhabited village, then on it and the rest of the find, one-fifth (khums) is payable.”

2. If the rikaz is found by someone in a land transferred to him, then it is his, as it is lodged in the land. Nevertheless, his ownership does not come from his possession of the land – it comes from the fact that it became known to him. Analogically, this kind of find falls into the category of grass, firewood, and game which are found on land which is not his. He can claim it if the one who transferred the land does not ask for it. In that case, it will be his because the land originally belonged to him. This is the view of Abu Yusuf, and the Hanbaliyyah uphold it as sound. Ash-Shaf’i says it belongs to the owner who transferred the land (if he claims it) before him, and so on until it is claimed by the first original owner.

Whenever land is transferred through inheritance, it is considered an inheritance by itself. If, however, the inhabitants agree that it did not belong to the one from whom they inherited it, then it belongs to the original owner. If he is unknown, then it is considered the lost property of an unknown owner. Abu Hanifah and Muhammad say that it belongs to the original owner of the land or to his inheritors if they are known; if they are not, it is to be placed in the public treasury.

3. If it is found in the land of a Muslim or a free non-Muslim subject (zhimmi), then it belongs to the owner of the land, according to Abu Hanifah, Muhammad, and Ahmad. It is also reported from Ahmad that it belongs to the one who found it (rikaz). Al-Hasan ibn Salih, Abu Thaur, and Abu Yusuf also preferred this opinion. This view is based on the belief that rikaz is not necessarily owned by the owner of the land, except when it is claimed by the owner. In such a case, his word will be the final one because he has the right over the land. If he does not claim it, it belongs to the one who finds it. AshShaf’i holds that it belongs to the one who claims it. Otherwise, it belongs to the original owner.