Is it permissible to swear a false oath to protect the rights of heirs who have not yet received their due, and to free witnesses from prison, knowing that the one swearing the oath is not denying the right of any heir and will give them their right?

It is not permissible to prevent an heir from their rightful share, for Allah Almighty says: {These are the limits [set by] Allah. And whoever obeys Allah and His Messenger will be admitted by Him to gardens [in Paradise] beneath which rivers flow, abiding eternally therein; and that is the great attainment. But whoever disobeys Allah and His Messenger and transgresses His limits – He will admit him to a Fire, abiding eternally therein, and he will have a humiliating punishment.} The enquirer must hasten to deliver the rights to the heirs. False testimony is among the greatest major sins, and one must repent from it, restore the rights to their owners, and declare the falsehood to whoever heard the false testimony. A false oath is also among the major sins, but it is permissible if it involves dissimulation to avert an injustice or reclaim a right.