Glossa Ordinaria

In prison. They who have their understanding darkened with shadows are deservedly said, even in this life, to be shut up in prison; and in this inward prison of the mind they are weighed down by unjust works, until, loosed from the flesh, they are cast into the exterior darkness of eternal damnation. The just also have a prison here, but one of tribulations; the reprobate, however, one of vices.