Q. Will all Christians be raised at the first resurrection or will some be raised at the first resurrection and some be raised at the end of the thousand years?
A. The resurrection is going to happen in stages and at different times. All believers will be in what is called the first resurrection even though it happens in stages and several thousand years apart in some cases. Once you know the stages you can read a verse and know when it is talking about. Dan 12.2 talks about the the righteous and unrighteous being raised but it may be thousands of years between the two. So, let's look at the stages. First, Yeshua was raised from the dead as we all know (Mt 28.1-7; Mk 16.1-11). But, what many fail to see is that others were resurrected within hours and were seen in the city (Mt 27.50-53). So, the first resurrection has already started. It's been two thousand years since that first stage but the next stage is coming up at the Natzal, or rapture, before the Tribulation period begins (1 Thes 4.13-18; 1 Cor 15.50-53). This will include every believer from creation and also those who are alive at the time. They will have their bodies changed to enter into the eternal state with the Lord and then return to earth with Him at His Second Coming. The bodies of all unbelievers will remain in the earth. In the middle of the Tribulation there will be the resurrection of the two witnesses (Rev 11.11-12). Then, at the beginning of the Messianic Kingdom those believers that died during the Tribulation will be raised (Rev 20.4-6). Those who survived the Tribulation will enter the Messianic Kingdom in natural bodies and were not killed when Yeshua returned and judged the nations (Mt 25). They will have children, but some will believe and others won't and this will go on for a thousand years. Lastly, at the end of the Messianic Kingdom, all unbelievers will be judged. Some will still be in natural bodies at the end of the thousand years but those who have died during the seven thousand years of human history will be raised at the Great White Throne judgment and stand before God (Rev 20.11-15). This is not for salvation but for judgment because they rejected eternal life. The resurrection of believers who died during the Messianic Kingdom is not mentioned in these verses but can be assumed. It could be that they are resurrected first and changed and will be present for the confirmation of their being justified by faith by the Lord. Their eternal state has been already assigned to them. Further light may be cast on this as the Messianic Kingdom goes along. After that, all unbelievers will be present and judged on their works because they rejected salvation by faith. As a result , they will be cast into the Lake of Fire, an eternal sate of separation from God and from that point God leads only those justified by faith into what is called the Olam Haba, or the World to Come. So, in conclusion, believers who have died will have a part in the first resurrection even though it happens in stages and at various times. Any unbeliever who has died will wait till the Great White Throne judgment and be raised and judged at that time.