Is it permissible for a husband to stipulate to his wife that she relinquish her deferred and prompt mahr (dowry) in exchange for taking her back after the second divorce, and does he have the right to threaten her with a third divorce at the first mistake?

Your husband does not have the right to stipulate, as a condition for your return, that you relinquish any part of your mahr (dowry) or your rights. His statement that he will issue the triple divorce at the first mistake is merely a promise, and divorce does not occur by it. We advise reconciliation and the intervention of wise family members to reunite the family and establish future understanding, especially since only one talaq (definition) (divorce pronouncement) remains.