Sin, Gehenna, and death do not exist at all with God, for they are effects, not substances. Sin is the fruit of free will. There was a time when sin did not exist, and there will be a time when it will not exist. Gehenna is the fruit of sin. At some point in time it had a beginning, but its end is not known. Death, however, is a dispensation of the wisdom of the Creator. It will rule only a short time over nature; then it will be totally abolished. Satan’s name derives from voluntarily turning aside from the truth; it is not an indication that he exists as such naturally.
St Isaac the Syrian. Extract from Ascetical Homily 27
Interesting! It seems a form of apokatastasis is in view here. I recall someone mentioning an association of Isaac with the concept, but hadn’t run across any citation. While he doesn’t come out and say it (by that point, you’d be labeled a heretic by defending the position), it is hinted: if Gehenna had a beginning, it’s going to have an end, at a time known or unknown. Most interestingly is the depiction of Satan as not inherently evil, or, in other words, as not incapable of repentance. With Gehenna gone, emptied of its prisoners, the implication is of the repentance of them all, as well as of Satan. Thus apokatastasis, or restoration of all to the Divine. Very interesting!