Is Zakat obligatory on money collected to help a brother pay off his debt, if a Hawl (lunar year) has passed over it?

Zakat is obligatory on the total amount if it reaches the nisab and a hawl (one lunar year) has passed on it, whether by itself or by adding it to other money or trade goods, regardless of the reason for its accumulation. However, if a hawl has not yet passed on it, there is no zakat due on it. The nisab for banknotes is the equivalent of 85 grams of gold or 595 grams of silver, and the amount of zakat that must be paid is a quarter of a tenth (2.5%).