The ruling on one who forgets or doubts regarding the payment of zakah

The questioner : Shaykh Muhammad, this is a woman calling in on the line. She says: A person forgot or doubted whether he paid the zakah on his wealth. Does he have to pay it a second time to address this doubt or this forgetfulness?

The Shaykh : Yes, if this person is one who has many doubts, then it is not obligatory for him to pay his zakah. But if he is not one who has many doubts, then he is required to pay it.

The questioner : If you please, possibly, and then if it was...

The Shaykh : If he had already paid it before, then the second payment is voluntary, and he will be rewarded by Allah for it. And if he had not paid it, then he has cleared his conscience by paying the second time.