Paul was in prison, but the word of God was “not bound” (2:10) because Paul could still write letters to the churches. So he was willing to “endure” prison for “the elect.” Christ is God’s elect, chosen by God to judge the Gentiles in the kingdom of heaven on earth (Isa.42:1 cf. Mt.18:18). Who else would He have chosen, an adulterous murderer like David. He demands rulers be just (cf.IISam.23:3).
But if God couldn’t choose sinners to rule in the kingdom, why’d the Lord tell the 12 they’d rule with Him (Mt.19:28) as well as other Tribulation overcomers (Rev.2:26)? Well, once they got saved they were as just as He was, and will be able to rule as justly as He will (Rev.3:21).
But God also chose Christ to rule the heavens, and us with Him (ICor.6:3). We’re not worthy to be chosen to rule either, but God chose us “in Him” (Eph.1:4). Now that we’re saved, we’re as just as he is (IICor.5:21) and can rule as justly as Him.
Paul was willing to endure prison so the elect could obtain salvation (2:10). The only other place that talks about obtaining salvation is a reference to the salvation of the Rapture (IThes.5:9 cf. Rom.11:13). Paul had to endure prison so they could obtain the Rapture “with eternal glory” (2:10), the kind we’ll get for suffering the sufferings of this present time with Christ (Rom.8:17,18). Suffering includes the light suffering of mocking (Gal.4:29 cf. Gen.21:9), light affliction that God plans to reward us for (IICor.4:17) if we keep our eye on the “unseen” glory we’ll receive (v.18) and so react to suffering in a godly and spiritual manner.
This suffering also includes the “pain” kind that Paul went on in Romans 8 to speak about (22,23). We don’t live under the law, when they had the chance to be spared pain and sickness (Deut.7:12-15), so God plans to reward us with glory for suffering pain. Since we all suffer pain, we’ll all be rewarded to some degree (ICor.4:5), if we keep our eyes on the unseen glory and react well to it.
To do that we need Paul’s epistles, and that’s why Paul was willing to suffer, to keep writing those epistles. He was ready to die earlier, but chose to stay because it was more “needful” for the saints for him to stay and finish his epistles (Phil.1:23-25). Once he knew he’d written them all he was “ready” to die (IITim.4:8).
To be eligible for glory you have to be saved though, so Paul reminds Timothy of this in 2:11, speaking about our identification with Christ in His death, burial and resurrection (cf.Rom.6:3-8).
If you are saved, you are eligible for the glory of reigning with Christ (2:12). We’ll all reign to some extent (ICor.4:5), but just as “one star differeth from another star in glory” (ICor.15:41), so some of us will shine brighter for the Lord. We have the opportunity to rule more angels, just as the Jews had the chance to rule more “cities” in the kingdom (Lu.19:17,19).
If that makes you uncomfortable, remember God has always wanted to glorify His people (Jer.30:19). Ultimately glorifying us glorifies Him (Phil.1:11). Just as every one of the stars glorifies its Creator no matter how strong or weak it shines, so will we.
We don’t have to suffer for the Lord, but if we “deny Him” our suffering, He’ll “deny us” the privilege of reigning with Him (2:12). Paul knows that some might think He means that He’ll deny us salvation, so He says that even if we get to the point where we don’t believe any more, we’re still saved (2:13). Think about that! The only thing you did to get saved was believe, and even if you stop doing that, “He cannot deny Himself.” You are part of Him (Eph.5:30) so to deny you He’d have to deny Himself.
If you think a true believer would never deny Him, you’re underestimating what the hard knocks of life can do to a believer’s faith. And what a lack of rightly dividing the Word can do! If you thought God promised you that you wouldn’t get sick if you were good (Deut.7:12-15), if you were good and got sick, it would shatter your faith too!