Is the husband required to verbally express his consent when the wife waives her rights in exchange for divorce, or is his implicit acceptance followed by divorce sufficient?

If a wife forgoes some of her financial rights to her husband so that he divorces her, and the husband agrees and divorces her, the divorce is irrevocably [ba'in] effective in exchange for what she has relinquished. It is not required for the husband to verbally express his agreement; his response by divorcing her is sufficient.