Is it permissible to reclaim and cultivate agricultural land that its owner abandoned forty years ago and emigrated?

It is not permissible to revive or reclaim land owned by someone else without the owner's permission, due to Allah's saying: (Do not consume one another's property wrongfully, but instead let there be trade by mutual consent among you), and the Prophet's (peace be upon him) saying: (The property of a Muslim is not lawful except with his willing consent), and (Indeed, your blood, your property, and your honor are sacred to you), and (Whoever usurps even a span of land will have it tied around his neck from seven earths).

If the owner is absent or dies without an heir, the land reverts to the state, and it is not permissible to dispose of it except with the state's permission. Therefore, you are not allowed to reclaim the land except by agreement with its owner, his agent, or his heirs.