Is Zakat obligatory on a sum of money deposited in a bank, knowing that it reaches the Nisab and a Hawl (full lunar year) has passed over it, despite continuous withdrawals and deposits from it?

Zakat (definition) is not obligatory on wealth unless it reaches the nisab (definition) and a full year (hawl) has passed on it. The nisab is approximately equal to eighty-five grams of pure gold, or five hundred ninety-five grams of pure silver. If the wealth reaches this amount and a full year passes on it, then Zakat is due on it at a rate of 2.5%. It is not permissible to deal with usurious banks. It is obligatory to withdraw money from them and dispose of the usurious interests by spending them on the welfare of Muslims or by giving them as charity to the poor and needy.