How is Zakah determined if only one partner's share reaches the Nisab?

Primary text

If the share of one partner reaches the Nisab while the other's does not, only the one whose share reached the Nisab is liable for Zakah, and this Zakah is due after the division. However, if the partner whose share did not reach the Nisab possesses other wealth that completes the Nisab from other sources, Zakah becomes obligatory upon both partners.