Is it permissible to divorce the second wife in order to recover a sum of money from the daughter's husband, then take her back, after offer and acceptance took place between them with the pronouncement of Khul' (divorce at the instance of the wife) in front of a lawyer?

If a person is threatened that they will not recover their large sum of money except by divorcing their wife, this constitutes duress, and a divorce under duress is not valid. Duress has conditions: the coercer must be capable (of carrying out the threat), it must be highly probable that the threat will be carried out, and the harm must be significant, such as the loss of a large sum of money. Khul‘ (divorce at the wife’s instance in return for compensation) under duress is also not valid. So, if the wife’s khul‘ is obtained to recover money, the marriage remains valid. In this situation, it is preferable to conclude a new marriage contract to officially document the marital bond.