When is emigration recommended (Mustahabb) but not obligatory?

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Emigration is recommended but not obligatory for one who is capable of leaving, yet can still manifest and practice their religion openly while dwelling in the land of disbelief. It is recommended so that such a person may engage in fighting (jihad) against them, increase the number of Muslims, and assist them, while also separating from the abundance of disbelievers, their mixing, and witnessing their evil. It is not obligatory because fulfilling the religious duties is possible without emigration, as evidenced by the residence of Al-Abbas, the uncle of the Prophet, peace be upon him, in Makkah after his conversion.