Is it permissible to pay the remaining deferred gold from the joint money saved from the spouses' salaries, or must it be from the husband's private money? And what is the ruling on the money that the wife contributes to household expenses, and is it considered a debt upon the husband, knowing that the wife forgives it?

The remaining value of the gold is a debt owed to the wife and must be paid, unless she voluntarily waives it. If the wife gives her husband money from her salary to dispose of as he wishes, explicitly stating that she does not intend to reclaim it, then it becomes his property, and he is permitted to buy gold with it. However, if she gives it to him solely to spend on the household, then he is not permitted to dispose of any remaining amount except in the manner intended by the wife.