Will he enter Paradise or Hell, then leave it or abide in it eternally—he who was a Christian by inheritance and convinced of Islam in his heart, but did not outwardly declare it for fear of being killed?

A person's mere conviction in Islam does not make him a believer except by his outward declaration, unless a legitimate coercion prevents him from manifesting it. Faith is the heart's affirmation, submission, and love. Thus, outward appearance without inner conviction is of no benefit, and inner conviction without outward appearance is insufficient, unless it is impossible due to incapacity or coercion. Legitimate coercion is that which compels, such as being threatened with death or with something unbearable. The coerced believer who died firm in his faith is considered a believer by Allah. A believer will not abide eternally in Hellfire, and may not enter it at all due to preventing factors such as repentance, expiating good deeds, intercession, and others.