[The Ruling on Giving to Beggars]

Answer—and Allah is the Granter of success: Allah the Exalted has made zakat obligatory and designated it for the poor, and it is not properly placed among the poor except after they are known. Thus, based on this, a person must ascertain the truth of their poverty if that is feasible; otherwise, a preponderant assumption (ẓann) of their poverty suffices.
Assumption may be formed by indicators. Hence Allah the Exalted said to His Prophet—May Allah bless him and his family and grant them peace: “[Give] to the poor who are restricted for the cause of Allah, unable to move about in the land. An ignorant person would think them self-sufficient because of their restraint, but you will know them by their [characteristic] sign. They do not ask people persistently.” [al-Baqarah:273]. Yes, the beggar has a right in one’s wealth if he is poor, Allah, Exalted is He, said: “And those within whose wealth is a known right—for the petitioner and the deprived.” [al-Maʿārij:24–25]; and, “And as for the petitioner, do not repel [him].” [al-Ḍuḥā:10]; and, “[Righteousness is] … to give wealth, in spite of love for it, to relatives, orphans, the needy, the traveler, those who ask, and for freeing slaves; [and] to establish prayer and to give zakah …” [al-Baqarah:177].
However, it is necessary to verify and be certain of the beggar’s poverty. It has been related that two men asked the Prophet—May Allah bless him and his family and grant them peace—for zakat, so the Messenger of Allah scrutinized them, looked them over carefully, and questioned them and sought clarification.
As for giving the beggar from zakat without verification, it is not appropriate—because of people’s great greed and the paucity of uprightness.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1