Who else but the elect can say these words? Can any reprobate truly say that they were united with Christ in His death and they frustrated the purpose of His death? Because from Gal 2:20 it is clear that the result from being united with Christ in His death is to live with and for Him. So much so that Paul says that He no longer lives, because he considers himself dead to sin and alive to God in Christ (Rom 6:11). When the Lord Christ died on the cross for our sin, we also died with Him. We were united with Him in His death and that is the assurance to Paul in Rom 6:5 that we also will be united with Him in the Resurrection.
Now we go back to 2 Corinthians, there the all are all who are in Him. All who are in the covenant which the Christ mediates. All whom He represents, all the elect. This is not the only time that Paul uses such a language, just take a look at a passage from 1 Corinthians 15 –
1Cor 15:22-23 For as in Adam all die, so also in Christ shall all be made alive. 23 But each in his own order: Christ the firstfruits, then at his coming those who belong to Christ.
It is clear what Paul is saying here. No need to go crazy about the “all's” because they are self-explanatory. What Paul is saying is clear. What he says is that in Adam all humanity which was represented by him in the Garden died (Rom 5:12ff). But in Christ all shall be made alive. There is not a single reason to believe that Paul had here in mind any other than the elect. This is seen from the those who will be resurrected. First of all, Christ was raised, but when He comes, at His Parousia, those who belong to Him. Not everyone who has ever lived. But specifically those who belong to Him, who have His Spirit in them (Rom 8:9), i.e. the elect, the Christians. They are the “all” who “shall be made alive” of verse 22. See 1 Corinthians 15:22-23, 'in Christ shall all be made alive'
So likewise in 2 Corinthians 5 Paul uses the same language. He does not mean every single human being, but all who are under the federal headship of Christ the Lord.
When He died, we died with Him, united to Him so that we may share in His Resurrection and life (Gal 2:20: Rom 6:3, 8; Col 2:20; 3:3; 2Tim 2:11).
Verse 15 gives us the purpose of His death. This is seen from the use of the ἵνα purpose clause. The ἵνα gives us the purpose and goal for a thing. Do not think that the rendering of ἵνα as “might” or “may” gives conditionality or uncertainty about a thing. The ἵνα may be translated as “that, in order that, so that.” It shows the purpose for the thing done.
The purpose of Christ's death was that the group for which He died, the “all”, may no longer live for themselves, i.e. in sin, but live for and in Him who for their sake died and was raised. Unless we want to say that God is frustrated in His purposes, which is impossible (Job 23:13; 42:2; Prov 19:21; Isa 14:27; Isa 46:10; Dan 4:35; Eph 1:11) we must accept that the group for which Christ died were the elect, i.e. the believers united with Him on the cross.
Many are the texts which speak of Christ specific and atonening death for the believers and that we will discusses when I try to present my case for Limited Atoneme...