Not totally sure but I’d think this to be a special placement particular to the apostles… those who “continued with Me in my trials”… those who ‘in the regeneration’ were to reign over Israel Lk 22:28-30 Mt 19:28.
Jesus came as Israel’s Redeemer (Mt 1:21; Lk 1:68; Rom 11:26-27) thus Israel’s covenantal restoration was his primary focus. This was not to the total exclusion of the Gentiles, BUT their inclusion was contingent upon Israel’s redemption; this order is reflected in part in Paul’s “to the Jew first then the Greek” ** Acts 3:26, 13:46; Rom 1:16, 2:10; 15:8**.
What was begun in Christ in terms of Israel’s redemption would be outworked to fullness in the Parousia in terms of Gentile inclusion and ultimate reconciliation… THROUGH the firstfruit saints aka “the Body of Christ”. Following on from the “mansions” comment to his disciples Jesus said, “greater works than these shall he do…” – not greater in magnitude but greater in scope. Jesus was but one, “they” however were the many; joined to Christ in the Spirit they would bring to fullness that which He began…
“What is lacking” – NOT in efficacy BUT in scope or reach. The disciples were appointed and anointed to become part of what Christ was doing ON BEHALF OF historic Israel and THEN in divine consequence on behalf of humanity beyond. Cf. Phil 1:29; 2Tim 4:6
This again is indicated here…
Again, back in the gospels Jesus had this to say…
This was the baptism of suffering… of laying down one’s life ON BEHALF OF the brethren (Israel – Rom 9:3, 10:1-2; 11:1-2, 28-29) that Paul & Co were called to fulfil. This “baptism” then answers to Pauls…
“The dead” of vs 12 is ‘Old Covenant Israel’ that Christ came to redeem. Some gentiles in Corinth were supposing that God had rejected and replaced Israel with them (replacement theology). Paul was saying “NO” – “IF Israel (the dead) rise not, of which was Christ, then surely neither has Christ been raised… and thus by implication neither have you!” I.e., “the root” supports you NOT the other way around! (Rom 11:18)
Again in Acts Paul demonstrates the unity of Christ’s mission WITH his firstfruits saints…
Get the gravity of this… this above is Isa 42:6; 49:6; Lk 2:32 with CLEAR prophetic reference to Christ and yet here is Paul (inspired) applying such prophetic words in fulfilment to themselves! How could Paul legitimately do this? Answer… the Disciples were “the Body of Christ” aka the “church of the firstborn” ones (‘firstborn’ is plural). Thus this joint work of Christ AND the firstfruit saints is seen…
Note Paul’s “through us”… as an extension of Christ to the degree that such was being cemented through them “to the glory of God.”