Is it permissible to count a sum of money you donated from your own wealth—without your husband's knowledge—as part of his vow, given that its value in Riyals might change when you pay the amount to your husband?

Vows of obedience must be fulfilled. If someone vows to donate a specific amount after getting a job, they are obliged to fulfill it. This type of vow is disliked (makrooh) but must still be fulfilled. If the husband did not specify the place for the vow, there is no harm in giving it in his home country in Saudi Riyals or its equivalent at the time of donation. It is not permissible to give a vow or Zakat (definition) on behalf of someone else without their knowledge, as intention is required for the obligation. However, some scholars hold that if the person learns about it after it has been given and approves it, then it is valid. Therefore, if the husband approves his wife's action in fulfilling the vow on his behalf, what she did is valid, and she is considered to have paid 2,0 Riyals on his behalf (the equivalent of 4,0 Egyptian Pounds). If this amount is his monthly salary, then he has fulfilled his vow; otherwise, he must pay the remaining amount. If the husband does not approve of her action, it is considered a charity from her, and his vow remains unfulfilled.