Praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
It is forbidden for the person who isn`t in need to beg people to give him charity and whatever he obtains via this means is unlawful because he got it through deception. Sharia has prohibited begging people for charity without being in need. This is attested to in the following Hadiths: Ibn ’Umar (RAA) narrated that The Messenger of Allah (PBUH) said: “A man who persists in begging people to give him charity, will come on the Day of Judgment and there will not be a piece of flesh on his face.” {Related by Bukhari & Muslim}. Moreover, it was narrated that Abu Hurairah said: "The Messenger of Allah said: "It is not permissible to give charity to a rich man (or one who is independent of means) or to one who is strong and healthy." {Related by Tirmithi}. In addition, Abu Hurairah (RAA) narrated that The Messenger of Allah (PBUH) said: “He who asks others to give to him in order to increase his own wealth, is akin to one who asks for live coals. He who wishes to have more, let him have it and he who wishes to have less, let him have it.” {Related by Muslim}.
In principle, a person must obtain his wealth lawfully, so wealth obtained unlawfully is equally unlawful. This is because the beggar is given charity under the assumption that he is needy and since he isn`t then that money isn’t his. "If a person gave charity to X thinking that he is Y, then he is permitted to take it back." {Hasheyat al-Shubramolsi ala Nehayat al-Mohtajj, V5:423}.
In conclusion, the wealth that a beggar accumulated from charities given to him under the assumption that he is needy, while he isn`t, aren`t considered his property. Thus, such money must be taken out of his estate and given to charity. And Allah the Almighty knows best.