Is the father who relinquished his children in exchange for fifty thousand Saudi Riyals (the deferred dower that the mother waived unconditionally) entitled to take his children when the mother marries another man?

These issues, which are matters of dispute and contention, cannot be resolved by a mere fatwa. The proper venue for their consideration is the Sharia court, because the judge can ascertain the positions of both parties and request evidence. The judge's ruling is binding and resolves disagreements in matters open to interpretation. Many issues related to custody are points of disagreement among jurists, including their disagreement on whether custody is a right of the custodian or a right of the child being cared for. From this stems the question of whether it is permissible to waive it or not, and similarly, whether it is permissible to take compensation for it or not, as well as whether it is permissible to revoke the waiver after it has been made. We advise consulting a Sharia judge regarding this matter.