Fr Jos Vanderlee, 65, agreed to let the man use the bathroom to clean himself on Sunday afternoon, officials said.
It's claimed the man became angry when the priest refused to give him money and pulled a knife on him in Lanaken, Eastern Belgium.
As the priest tried to defend himself and disarm the man he received stab wounds to his hands.
Prosecutors said it was not related to terrorism.
Local mayor Marino Keulen is quoted by local media as having said: "Despite the fact that we are shocked, we must stress that this incident cannot be linked to terrorist acts at this stage of the investigation."
The priest's injuries are not life threatening.
