Is the 100 years symbolic? When will this event take place?
The setting of Isaiah 65 is a prophecy about the time when the Kingdom of God will govern the entire world. The book of Revelation complements many Old Testament prophecies, including this one. Revelation 20:5 tells us that there will be a resurrection after the first 1,000 years of Christ's reign. Verses 11-13 add more detail, explaining that God will bring people who were not called to salvation during their initial lifetime back to life again.
In the Church of God, we often refer to this time as the Great White Throne Judgment, because of the description of God's throne in these verses. How long is this period? These verses in Revelation do not tell us. Instead, they focus on the purpose for it—to give everyone an opportunity to respond to God's calling and to live the Christian way of life.
Some have said that God intends to show us through Isaiah 65:20, where the phrase "one hundred years" appears twice, that this time frame is 100 years. That may be the case, or it may be a way to emphasize the same principle given in Revelation 20. That is, the people will have the time that they need to respond to God's calling and live the Christian way of life. "One hundred years" may be a way of making that point, rather than a literal prophecy.
Due to the limited evidence available, the Church cannot say with certainty that this will be a total of 100 years. There are different alternatives for interpreting this verse, while maintaining the teaching of three resurrections. The following is an excerpt from our "Resurrections" study paper.
1. The Great White Throne Judgment will last for 100 years. The Church of God has taught that this will be a testing period of 100 years, during which billions of children and adults would have an opportunity to inherit eternal life. Therefore the death of the "sinner being one hundred years old" has been considered to be the second death. God certainly could do things this way if He so chooses.
2. Life spans will exceed 100 years during the Great White Throne Judgment. This verse certainly conveys a time of longevity, though not necessarily an exact "one hundred years." Isaiah 65:20 says, "No more shall an infant [ uwl , 'suckling'] from there live but a few days ... For the child [ naar , 'young, youth, young man'] shall die one hundred years old " ( Enhanced Strong's Lexicon , Logos Research Systems, Inc., 1995). This could be describing pre-Flood-type conditions where 100 years are a small portion of one's life. If so, then those who are only 100 years old will be considered a "child, youth" or "young man" at 100 years old. And to die at this age would be analogous to a premature death.
3. Isaiah 65:20 describes a time during the Millennium. If so, then this would provide plenty of time for the pre-Flood-type extended life spans (see above). Under this scenario, one might expect the same type of life spans during the Great White Throne Judgment time period.