HannibalFlavius said in post 271:
To once again unite Gentiles with Jews into one man.
Note that this doesn't have to happen "once again", because it's spiritually been the case continuously from the beginning of the church down until this day. For just as all genetic Jews in the church have always remained members of whichever tribe of Israel they were born into (Romans 11:1, Acts 4:36), so all genetic Gentiles in the church have always been spiritually grafted into Israel (Romans 11:17,24, Ephesians 2:12,19, Galatians 3:29), and so have been grafted into its various tribes (cf. Ezekiel 47:21-23). So the entire church has always been the 12 tribes of Israel (Revelation 21:9,12; 1 Peter 2:9-10).
This has always been necessary, for all those in the church have always been saved only by the New Covenant (Matthew 26:28; 1 Corinthians 11:25; 2 Corinthians 3:6, Hebrews 9:15), and the New Covenant is made only with Israel (Jeremiah 31:31-34, John 4:22b). John 10:16 refers to the "other sheep" of believers who are Gentiles being brought into "this fold" of Israel, which is the same as the "one fold" of the church (1 Corinthians 12:13, Ephesians 4:4-6, Revelation 21:9,12). A genetic Gentile believer can pray and ask which tribe of Israel he has been grafted into, and he will receive an answer from God, if he asks in faith (cf. Matthew 21:22), without any wavering (cf. James 1:6-7).
Also, all those in the church, no matter whether they're genetic Jews (Acts 22:3) or genetic Gentiles (Romans 16:4b), have always become spiritually-circumcised Jews if they've undergone the spiritual circumcision of water-immersion (burial) baptism into Jesus (Romans 2:29, Philippians 3:3, Colossians 2:11-13).
HannibalFlavius said in post 271:
To once again unite Gentiles with Jews into one man.
It's sometimes claimed that this can only happen by Gentiles observing the letter of the Old Covenant Mosaic law. But the truth is that on Jesus' cross, for both Jews and Gentiles (John 11:51-52), of all times, the letter of the Old Covenant Mosaic law was abolished (Ephesians 2:15-16, Colossians 2:14-17; 2 Corinthians 3:6-18), disannulled (Hebrews 7:18), rendered obsolete (Hebrews 8:13, Galatians 3:2-25, Galatians 4:21 to 5:8), taken away and replaced (Hebrews 10:9) by the better hope (Hebrews 7:19), the better covenant (Hebrews 7:22, Hebrews 8:6-12), the 2nd covenant (Hebrews 8:7, Hebrews 10:9), of Jesus' New Covenant law (Galatians 6:2, John 1:17, Matthew 26:28, Hebrews 12:24, Hebrews 9:15), so that the law was changed (Hebrews 7:12).
All believers, both Jews and Gentles, of all times, are delivered from the letter of the Old Covenant Mosaic law and shouldn't keep it (Romans 7:6; 2 Corinthians 3:6-18, Galatians 2:11-21) or have any desire to keep it (Galatians 4:21 to 5:8, Galatians 3:2-25). Believers keep the spirit of the Old Covenant Mosaic law (Romans 7:6) by loving others (Galatians 5:14, Romans 13:8-10), by doing to others as they would have others do to them (Matthew 7:12).
The New Covenant is a new law (Hebrews 7:12,18,19, Hebrews 10:1-23), consisting of Jesus' New Covenant/New Testament commandments (John 14:15), such as those he gave in the Sermon on the Mount (Matthew 5:19 to 7:29) and in the epistles of Paul the apostle (1 Corinthians 14:37). These commandments exceed in righteousness the abolished letter of the Old Covenant Mosaic law (Matthew 5:20-48). So there's no reason why any believer should ever want to go back under the letter of the Old Covenant Mosaic law (Galatians 3:2 to 5:26). It was just a temporary schoolmaster (Galatians 3:24-25), a temporary shadow (Colossians 2:16-17), which God set up because of sins long after he'd set up the original promise of the Abrahamic Covenant, and long before he brought that promise to fulfillment in Jesus' New Covenant (Galatians 3:16-29, Matthew 26:28).
The letter of the Old Covenant Mosaic law has been made obsolete by the New Covenant (Hebrews 8:13). For example, the letter of the Old Covenant Mosaic law required an Aaronic priesthood (Exodus 30:30), whereas the New Covenant replaced the Aaronic priesthood with the Melchisedechian priesthood (Hebrews 7:11-28). Also, the letter of the Old Covenant Mosaic law required animal sacrifices (e.g. Leviticus 23:19), whereas the New Covenant replaced those with the one-time sacrifice of Jesus (Hebrews 10).
The letter of the Old Covenant Mosaic law is the Hagar to the New Covenant's Sarah (Galatians 4:22-25), so that those people, whether Jews or Gentiles, who try to keep the letter of the Old Covenant Mosaic law are like Ishmael, while those people, whether Jews or Gentiles, who keep the New Covenant are like Isaac (Galatians 4:22-31).
The letter of the Old Covenant Mosaic law (including the letter of the 10 commandments), written and engraven in stones (2 Corinthians 3:7, Deuteronomy 4:13, Deuteronomy 27:8), was the ministration of death and condemnation (2 Corinthians 3:7,9). For example, see Leviticus 20:10, Exodus 31:14, and Numbers 15:32-36; and contrast these with the New Covenant's John 8:4-11 and Matthew 12:1-8. The letter of the Old Covenant Mosaic law has been done away (2 Corinthians 3:11), abolished (2 Corinthians 3:13b). But it's still able to spiritually blind some people as with a veil from beholding Jesus (2 Corinthians 3:14-16), whereas the New Covenant is the ministration of the spirit and righteousness (2 Corinthians 3:6,8,9b), which remains (2 Corinthians 3:11b), and which permits believers to remove the veil and to behold Jesus (2 Corinthians 3:16-18, Mark 15:38, Hebrews 7:18-19, Ephesians 2:15-18, Colossians 2:14-17).
But a mistaken spirit of Pharisaism can still sometimes deceive even Christians into thinking that they must keep the letter of the Old Covenant Mosaic law in order to be saved (Acts 15:1,5), or in order to become perfect (Galatians 3:2 to 5:26). This is a false, cursed gospel (Galatians 1:6-9). For if any believers are keeping any part of the letter of the Old Covenant Mosaic law, thinking that they must do so in order to be saved, or in order to become perfect, then Jesus will profit them nothing; they have fallen from grace (Galatians 5:2-8).