From which asset should Zakah be paid when a full Hawl (lunar year) has passed on trade goods?
Chapter on Zakat on Sheep
Al-Mughni
Book of Zakat
Primary text
Zakah must be paid from the commodity that was sold, not from the capital currently in possession. This is because Zakah became obligatory specifically due to that sold asset; without it, Zakah would not have been required on this type of wealth.