II. What is meant by prison here? Purgatory, or the limbus patrum, say the Romanists - a place in which departed souls are supposed to be confined, and in which their final destiny may still be effected by the purifying fires which they endure, by the prayers of the living, or by a message in some way conveyed to their gloomy abodes - in which such sins may be expiated as do not deserve eternal damnation. The Syriac here is “in Sheol,” referring to the abodes of the dead, or the place in which departed spirits are supposed to dwell. The word rendered “prison,” (φυλακῇ phulakē,) means properly “watch, guard” - the act of keeping watch, or the guard itself; then watchpost, or station; then a place where anyone is watched or guarded, as a prison; then a watch in the sense of a division of the night, as the morning watch. It is used in the New Testament, with reference to the future world, only in the following places: 1Pe_3:19, “Preached unto the spirits in prison;” and Rev_20:7, “Satan shall be loosed put of his prison.”
An idea similar to the one here expressed may be found in 2Pe_2:4, though the word prison does not there occur: “God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;” and in Jud_1:6, “And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains, under darkness, unto the judgment of the great day.”
When 1Pe_3:19 speaks of 'prison', isn't he talking about hell though...rather than some sort of purgatory? As I understand it, Purgatory is a Roman Catholic teaching that describes a temporary place of punishment. In general don't protestant churches reject the doctrine of purgatory?
And this prison then,... surely this isn't necessarily the abode of the OT saints. It seems rather that the prison is the likely destination of the fallen angels (2 Peter 2:4) that God cast down into hell...the angels that rebelled against God.