What is the ruling on someone who pays Zakat to purchase medicine for a sick person, only to find out later that the person sells the medicine and is lying?

The medicine given by the questioner to those claiming illness is not considered a valid zakat if he calculates it as such, except under two conditions:

1. The intention of zakat is made before or at the time of giving the medicine.

2. Those claiming illness are genuinely poor and in need. If it becomes clear that they are wealthy, then the zakat must be given again. This is the view of the Shafi'i school. The questioner is advised not to rush into paying zakat to those who are not eligible. If he cannot reach the deserving recipients, he can give it to charitable organizations or individuals who will deliver it to those who are eligible.