What is the ruling on kidnapping the children of apostates to extort money from them?

The ruling of apostasy on a person is not a light matter, as it requires that he commit acts necessitating apostasy, that proof be established against him, that the conditions for declaring someone a disbeliever be met, and that the obstacles to doing so be absent. It is not for the general public to rule on apostasy or to carry out the prescribed punishment; rather, this is the exclusive prerogative of the Sharia judiciary, and its implementation falls under the authority of the Muslim ruler. Assaulting his children by kidnapping or similar acts is an injustice and holding an innocent person accountable for another's sin, which is forbidden.