Can the debt of six thousand dirhams that you owed to your spouse be considered the fulfillment of the vow to donate five thousand dirhams as charity after marriage?

Waiving a debt in lieu of a vow is not permissible and does not absolve the debtor. The money owed must be collected first, then given to the needy husband. Charity requires actual possession [of the funds], and waiving a debt is not sufficient. If it is impossible to recover the amount, then the vow must be fulfilled by donating the equivalent amount to the husband or other deserving recipients.