He found an amount of cash in the Haram (in Makkah)

Praise be to Allah.

The scholars differed with regard to lost property found in the Haram: is it like lost property found elsewhere, which the finder may keep after announcing it and looking for its owner for one year, or can it never become the property of another? Some scholars said that the finder can keep it because of the general meaning of the hadeeth; others said that he cannot keep it, and the search to identify the owner should continue indefinitely, because the Prophet (peace and blessings of Allaah be upon him) said concerning Makkah, “It is not permissible for anyone to keep lost property found there except the one who claims it by identifying it properly.” Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) favoured the latter opinion, and said: “He should not keep it at all, because that is forbidden, and it should be announced indefinitely in a search to identify the owner.” This is the apparent meaning of the report which says it is forbidden.

Al-Mulakhkhas al-Fiqhi by Saaalih al-Fawzaan, 150.

Shaykh Ibn ‘Uthaymeen was asked the following question: is it permissible for me to pick up lost property in Makkah and take it and announce it in the area where I live, or do I have to announce it at the doors of the mosque and market-places etc. in Makkah itself?

He answered, may Allâh preserve him: the case of lost property in Makkah is unique in that it is not permissible for anyone to pick it up except the one who wants to announce it indefinitely or hand it over to those who are in charge of such things, because the Prophet (peace and blessings of Allaah be upon him) said, “It is not permissible to pick up lost property except for the one who wants to announce it.” The reason behind this is that if the lost property is left where it is, its owner will probably come back and find it. On this basis, we say to this brother: you have to announce it in Makkah, in and around the place where you found it, such as at the doors of the mosque and in places where people gather, otherwise you should hand it in to those whose job it is to take care of lost property etc. Fatawa Islamiyah, 2/311.

And Allâh knows best.