Is it Islamically permissible for the father to deny the mother visitation rights to her son after she has relinquished her right to custody and he has traveled with the child for three years?

The mother's relinquishment of child custody in exchange for divorce is a matter of scholarly disagreement. The majority view is that this condition is invalid. It is not permissible for the custodian to prevent the other party from seeing and visiting the child. In case of dispute, the matter should be referred to the Sharia judge to regulate visitation. The father should fear Allah and not deprive the mother of seeing her child.