Sheikh Sulaymân al-Tuwayjirî
The person should take sufficient care to ensure that those to whom he gives his Zakâh are eligible to receive it.
Zakâh should be given only to the categories of recipients mentioned in the verse of Zakâh. It reads: “Alms are only for the poor and the needy, and the officials (appointed) over them, and those whose hearts are to be reconciled, and to free the captives, and for those in debt, and for the cause of Allah, and the wayfarer; an ordinance from Allah; and Allah is knowing, Wise. [Sûrah al-Tawbah: 60].
The person should be as careful as possible. However, if after exercising due diligence in the matter, he unintentionally pays his Zakâh to someone who is ineligible to receive it, then his obligation will be fulfilled and he will not have to pay it again.
If you see a person to be deserving of Zakâh and pay it to him, then you have done the right thing by giving it to him, even if you discover later on that he was lying.
May Allah guide us all.
Source: Islam Today