Slaughtering some of the sheep for a guest before the completion of the lunar year and its effect on zakah

Question:
Honorable Shaykh, may Allah grant you success. If a person has forty sheep and a guest comes to him, so he slaughters a sacrificial animal for him before the completion of the lunar year, does the zakah become due in this case?

Answer:
Yes, the zakah is not due if the number falls below the nisab (minimum threshold for zakah) before the completion of the lunar year. Slaughtering it for the guest is a need; he slaughtered it for the need, not to escape the zakah. He slaughtered it for his need, and this is permissible. However, if he slaughters it after the lunar year has completed, the zakah becomes obligatory upon him, even if the number falls below the nisab; because it did not fall below the threshold except after the zakah had become due.