What if a man who testifies that there is no God but Allah and offers the Salah (prayer), but does not pay the Zakat?
A person did not pay zakat for four years; what is incumbent upon him? Answers: As all Muslims should know, zakat is a duty that will not fall until it is executed. The delay in paying zakat mostly either because of the loss of wealth or maybe because of own ignorance.
Malik said that a collector wrote to 'Umar bin Abdul Aziz complaining about a man who refused to pay zakat. 'Umar wrote that he should leave him alone and not take his zakat from him with the other Muslims. When the man heard of this, he felt pained and paid the zakat on his property. The collector then wrote to 'Umar making mention of this fact, and 'Umar bin Abdul Aziz wrote back (asking him) to take his zakat [Refer Muwatta Imam Malik: 1/270]
Orang yang enggan menunaikan zakat, padahal dia berkeyakinan hukumnya wajib, maka penguasa harus memungut zakatnya secara paksa...