Alms Tax: Giving Zakat to a Beggar and for Sinful Purposes
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1959
A person can give zakat to a poor person who begs provided that the fact of his poverty is established. However, one must not give zakat to a person who spends it for sinful purposes. In fact, the obligatory precaution is that zakat must not be given to someone who, as a result of receiving it, will be encouraged to commit sins even if he does not spend it directly for sinful purposes.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)