Does a Muslim pay Zakat on all of his sheep when a year has passed on his old sheep, or does he wait for a year to pass on the sheep bought on installments?

A man is to pay zakat on his new sheep after a full year (hawl) has passed since their purchase, and not combine them with his old sheep. This is the view of some scholars, such as the Hanbalis and Shafi'is, and he is permitted to follow this madhhab. However, if he pays zakat on them together with his old sheep, it is more preferable to avoid scholarly disagreement. As for debt, it does not waive the obligation of zakat on sheep.